Perfluoroelastomer compositions and methods of preparing same

ABSTRACT

The present invention includes crosslinked perfluoroelastomeric compositions and molded articles formed from a cross-linkable perfluoroelastomeric composition having a first curable perfluoropolymer having a cure site monomer and a second perfluoropolymer having a cure site monomer. The molar ratio of the tetrafluoroethylene monomer to perfluoroalkylvinyl ether in one perfluoropolymer is about 0 to 100 to about 65 to 35 in the perfluoropolymer. The molar ratio of the tetrafluoroethylene monomer to the perfluoroalkylvinyl ether monomer in the second polymer is about 65:35 to about 95:5 in the second perfluoropolymer. The composition further includes a curative. One fluorine-containing elastomer composition herein, having a short crosslinking time, has perfluoroelastomers (A) having a tetrafluoroethylene unit, a perfluoralkylvinyl ether unit (a) and a monomer unit (b) having at least one kind selected from the group consisting of a nitrile group, a carboxyl group and an alkoxycarbonyl group, wherein the composition has two or more kinds of perfluoroelastomers (A) having differing contents of perfluoroalkylvinyl ether unit (a).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fluorine-containing elastomercomposition prepared using perfluoroelastomers having different contentsof a perfluoro(alkyl vinyl ether) unit, and a sealing material made ofthe composition. The present invention also relates to curablecompositions and the molded articles of perfluoroelastomers (FFKM)having excellent thermal and plasma resistance.

2. Description of Related Art

Fluorine-containing elastomers, particularly perfluoroelastomers mainlycomprising tetrafluoroethylene (TFE) unit exhibit excellent chemicalresistance, solvent resistance and heat resistance, and therefore arewidely used for a sealing material, etc. used under strict environments.

However with advances in technologies, the characteristics required havebeen made more rigorous, and in the fields of aeronautics, spaceindustries, semiconductor manufacturing equipment and chemical plant,sealing property under a high temperature environment of not less than300° C. is demanded.

Accordingly, for improving the curing speed, Japanese Patent DocumentJP2001-504885A discloses a curable composition prepared by adding acuring accelerator such as an organic or inorganic ammonium salt to amixture of a perfluoro elastomer and a curing agent.

Perfluoroelastomeric materials are known for their chemical resistance,plasma resistance, and when used in compositions having typical filleror reinforcing systems for acceptable compression set resistance levelsand mechanical properties. As such, they have been applied for manyuses, including for use as elastomeric sealing materials in applicationswhere a seal or gasket will be subject to highly corrosive chemicalsand/or extreme operating conditions, and for use in forming molded partsthat are capable of withstanding deformation. FFKMs are also well knownfor use in the semiconductor manufacturing industry as sealing materialsdue to their chemical and plasma resistance. Such materials aretypically prepared from perfluorinated monomers, including at least oneperfluorinated cure site monomer. The monomers are polymerized to form aperfluorinated polymer having the cure sites from the cure sitemonomer(s) and then cured (cross-linked) to form an elastomer. TypicalFFKM compositions include a polymerized perfluoropolymer as noted above,a curing agent that reacts with the reactive cure site group on the curesite monomer, and any desired fillers. The cured perfluoroelastomerexhibits typical elastomeric characteristics.

FFKMs are generally known for use as O-rings and related sealing partsfor high-end sealing applications due to their high purity, excellentresistance to heat, plasma, chemicals and other harsh environments.Industries that require their use in such environments includesemiconductor, aerospace, chemical and pharmaceutical. The developmentof new perfluoroelastomer compositions using these materials facesever-increasing demands and challenges for FFKMs and compositions basedon FFKMs that have the ability to provide greater thermal, chemical andplasma resistance. Industry demands, particularly in the semiconductorarea continue to require enhanced performance of such seals to meet newend-use applications that have increasingly aggressive environments aswell as lower and lower contamination and particulation requirements.

As is recognized in the art, different FFKM compositions may includedifferent curatives (curing agents) depending on the type of cure sitemonomer (CSM) structure and corresponding curing chemistry. Suchcompositions may also include a variety of fillers and combinations offillers to achieve target mechanical properties, compression set orimproved chemical and plasma resistance. For semiconductor sealingapplications, both inorganic and organic fillers can be used to improveplasma resistance depending on the type of plasma chemistry. Typicalfillers include carbon black, silica, alumina, fluoroplastics, bariumsulfate and other plastics. Fillers used in some FFKM compositions forsemiconductor applications include fluoroplastic filler particles formedof polytetrafluoroethylene (PTFE) or melt-processible perfluorinatedcopolymers such as copolymers of tetrafluoroethylene (TFE) andhexafluoropropylene (HFP) (also referred to as FEP-type copolymers) orof TFE and perfluoroalkylvinyl ethers (PAVEs) (known as PFA-typecopolymers), particularly in nanomer-sized particles.

U.S. Pat. No. 6,710,132 discloses a blend of an FFKM withsemi-crystalline fluoroplastic particles (such as PTFE), wherein theparticles have a core-shell structure and are formed by latex blendingof these materials.

U.S. Pat. No. 4,713,418 discloses a composition formed by melt blendingan FFKM and a melt-processible thermoplastic fluoropolymer. The patentasserts that particles of about 10 microns are reformed from some of themelted thermoplastic upon recrystallization. U.S. Patent Publication No.2005/0261431 A1 discloses melt blending an FFKM and a semicrystallinepolymer such as PTFE and/or a copolymer, such as the PFA-type copolymer,of greater than an average size of 100 nm wherein blending temperatureor curing temperature exceeds the melting temperature of thefluoroplastic fillers.

U.S. Pat. No. 7,019,083 and International Publication WO2006/120882 A1disclose crosslinkable fluoroplastics.

When an FFKM composition includes a semicrystalline fluoroplasticparticle filler, such as microparticles or nanoparticles of PTFE orcopolymers such as those of the PFA-type, good physical properties, goodplasma resistance and excellent purity are achieved. For semiconductorapplications, such systems also help to avoid metallic particulation andcontamination at a level improved over FFKMs, which have inorganicfillers such as metal oxides. However, there is a need in the art todevelop more simplified processing methods to form fluoropolymer-filledFFKMs. Latex blending can be expensive for large-scale, commercialbatches and melt blending generally requires temperatures of up to 350°C. Filler loading in many commercial products is generally limited to upto about 30 weight percent of the base polymer. Due to the use of thefluoropolymeric fillers, such compositions can also sometimes have arelatively high compression set especially at high temperatures(e.g., >300° C.). Moldability and bondability can also be limited due touse of such fluoropolymeric fillers.

There is a need in the art for further improvements toperfluoroelastomer compositions which, upon cure, provide high thermalresistance, low compression set, good plasma resistance, relatively lowhardness, sufficient strength and elongation which meet the increasinglydemanding requirements for use in high-end sealing applications likethose of semiconductor processing.

BRIEF SUMMARY OF THE INVENTION

Problem to be solved by the invention: It is an object of the presentinvention to provide a fluorine-containing elastomer compositionassuring a short crosslinking time. The means to solve the problem: Inthe present invention, attention was directed to a problem that acrosslinking time is longer when a perfluoroelastomer having a smallcontent of a perfluoroalkylvinyl ether unit is used.

Namely, the present invention relates to a fluorine-containing elastomercomposition comprising perfluoroelastomers (A) having atetrafluoroethylene unit, a perfluoroalkylvinyl ether unit (a) and amonomer unit (b) having at least one kind selected from the groupconsisting of a nitrile group, a carboxyl group and an alkoxycarbonylgroup, wherein the composition comprises two or more kinds ofperfluoroelastomers (A) having different contents of theperfluoroalkylvinyl ether unit (a).

It is preferable that in two or more kinds of perfluoro elastomers (A),a difference in the content of perfluoroalkylvinyl ether unit (a)between any two kinds of perfluoroelastomers (A) is 5 to 25% by mole.

The monomer unit (b) is preferably a nitrile group-containing monomerunit.

The perfluoroalkyl vinyl ether unit (a) is preferably a perfluoromethylvinyl ether unit.

It is preferable that the fluorine-containing elastomer compositionfurther comprises a crosslinking agent (B) being crosslinkable with atleast one kind selected from the group consisting of a nitrile group, acarboxyl group and an alkoxycarbonyl group of the monomer unit (b).

An amount of the crosslinking agent (B) is preferably 0.3 to 10.0 partsby mass based on 100 parts by mass of the whole perfluoro elastomers.

The crosslinking agent (B) is preferably a compound containing at leasttwo crosslinkable reaction groups represented by the formula (II):

wherein R¹ are the same or different and each is —NH₂, —NHR₂, —OH or—SH; R² is a monovalent organic group,

a compound represented by the formula (III):

wherein R³ is —SO₂—, —O—, —CO—, an alkylene group having 1 to 6 carbonatoms, a perfluoroalkylene group having 1 to 10 carbon atoms or a singlebond; R⁴ is

a compound represented by Formula (IV):

wherein R_(f) ¹ is a perfluoroalkylene group having 1 to 10 carbonatoms, and a compound represented by the formula (V):

in which n is an integer of 1 to 10.

The present invention also relates to a sealing material forsemiconductor manufacturing equipment made of the above-mentionedfluorine-containing elastomer composition.

The effect of the invention is that the present invention can provide anelastomer composition for crosslinking which assures a shortcrosslinking time and gives a crosslinked rubber molded article.

Described herein is a fluorine-containing elastomer composition whichincludes a first curable perfluoropolymer comprisingtetrafluoroethylene, a first perfluoroalkylvinyl ether and at least onefirst cure site monomer having at least one functional group selectedfrom the group consisting of nitrile, carboxyl and alkoxycarbonyl, and asecond curable perfluoropolymer comprising tetrafluoroethylene, a secondperfluoroalkylvinyl ether and at least one second cure site monomerhaving at least one functional group selected from the group consistingof nitrile, carboxyl and alkoxycarbonyl, wherein the content of thefirst perfluoroalkylvinyl ether in the first curable perfluoropolymerand the content of the second perfluoroalkylvinyl ether in the secondcurable perfluoropolymer are different.

The fluorine-containing elastomer composition may include at least oneadditional curable perfluoropolymer comprising tetrafluoroethylene, aperfluoroalkylvinyl ether and a cure site monomer.

Further, in preferred embodiments, the content of the firstperfluoroalkylvinyl ether in the first curable perfluoropolymer differsfrom the content of the second perfluoroalkylvinyl ether in the secondcurable perfluoropolymer by about 5 to about 25 molar percent.

The functional group of the first cure site monomer and/or thefunctional group of the second cure site monomer in thefluorine-containing elastomer composition is preferably a nitrile groupand the first perfluoroalkylvinyl ether and/or the secondperfluoroalkylvinyl ether is preferably perfluoromethylvinyl ether.

A curing agent may be provided to the fluorine-containing elastomercomposition which curing agent is capable of crosslinking with thefunctional group of the first cure site monomer and/or the functionalgroup of the second cure site monomer. It may be added in an amount ofthe curing agent of about 0.3 to about 100 parts by weight per 100 partsby weight of the first curable perfluoropolymer and the second curableperfluoropolymer combined.

The curing agent may be selected from various compounds, such as

a compound having at least two crosslinkable reaction groups accordingto formula (II):

wherein each R¹ group is the same or different and each is selected from—NH₂, —NHR², —OH or —SH, wherein R² is a monovalent organic group;

a compound according to formula (III)

wherein R³ is —SO₂—, —O—, —CO—, an alkylene group of from 1 to about 6carbon atoms, a perfluorinated alkylene group of from 1 to about 10carbon atoms or a single bond, wherein R⁴ is

a compound according to formula (IV):

wherein R_(f) ¹ is a perfluoroalkylene group of 1 to about 10 carbonatoms; and

a compound according to formula (V):

wherein n is an integer of 1 to about 10.

The invention may include a sealing material for use in semiconductormanufacturing equipment made using the fluorine-containing elastomercomposition as noted above.

The invention further includes a curable perfluoroelastomericcomposition comprising: a first curable perfluoropolymer comprisingtetrafluoroethylene, a first perfluoroalkylvinyl ether and at least onefirst cure site monomer having a cure site, wherein a molar ratio of thetetrafluoroethylene to the perfluoroalkylvinyl ether is about 0:100 toabout 65:35 molar percentage in the perfluoropolymer; a second curableperfluoropolymer comprising tetrafluoroethylene, a secondperfluoroalkylvinyl ether which may be the same or different from thefirst perfluoroalkylvinyl ether, and at least one second cure sitemonomer having a cure site which may be the same or different from theat least one first cure site monomer, wherein a molar ratio of thetetrafluoroethylene to the second perfluoroalkylvinyl ether is about65:35 to about 95:5 in the polymer; and at least one curative capable ofcuring the at least one first cure site monomer and the at least onesecond cure site monomer.

In one embodiment, in the curable composition first curableperfluoropolymer comprises about 0 to about 58.5 mole percent of thetetrafluoroethylene, about 31.5 percent to about 99.99 mole percent ofthe first perfluoroalkylvinyl ether and about 0.1 mole percent to about10 mole percent of the at least one first cure site monomer and thesecond curable perfluoropolymer comprises about 65 to about 85.5 molepercent of the tetrafluoroethylene, about 4.5 to about 35 mole percentof the second perfluoroalkylvinyl ether and about 0.1 mole percent toabout 10 mole percent of the at least one second cure site monomer.

The invention also includes a cured perfluoroelastomeric composition,comprising: a first perfluoroelastomer formed from a first curableperfluoropolymer comprising tetrafluoroethylene, a firstperfluoroalkylvinyl ether and at least one first cure site monomerhaving a cure site, wherein a molar ratio of the tetrafluoroethylene tothe perfluoroalkylvinyl ether is about 0:100 to about 65:35 molarpercentage in the perfluoropolymer; and a second perfluoroelastomerformed from a second curable perfluoropolymer comprisingtetrafluoroethylene, a second perfluoroalkylvinyl ether which may be thesame or different from the first perfluoroalkylvinyl ether, and at leastone second cure site monomer having a cure site which may be the same ordifferent from the at least one first cure site monomer, wherein a molarratio of the tetrafluoroethylene to the second perfluoroalkylvinyl etheris about 65:35 to about 95:5 in the second curable perfluoropolymer.

The invention also includes molded articles comprising a curedperfluoroelastomeric composition, wherein the composition comprises afirst perfluoroelastomer formed from a first curable perfluoropolymercomprising tetrafluoroethylene, a first perfluoroalkylvinyl ether and atleast one first cure site monomer having a cure site, wherein a molarratio of the tetrafluoroethylene to the first perfluoroalkylvinyl etherin the first curable perfluoropolymer is about 0:100 to about 65:35; anda second perfluoroelastomer formed from a second curableperfluoropolymer comprising tetrafluoroethylene, a secondperfluoroalkylvinyl ether which may be the same or different from thefirst perfluoroalkylvinyl ether, and at least one second cure sitemonomer having a cure site which may be the same or different from theat least one first cure site monomer, wherein a molar ratio of thetetrafluoroethylene to the second perfluoroalkylvinyl ether in thesecond curable polymer is about 65:35 to about 95:5.

Such molded articles herein may be sealing members that can be bonded toa surface comprising a metal or a metal alloy such as to a surface of adoor for sealing a semiconductor processing chamber or other reactionchamber.

The invention further includes a method for making a curedperfluoroelastomeric composition comprising: (a) preparing a curableperfluoroelastomeric composition by combining: (i) a first curableperfluoropolymer comprising tetrafluoroethylene, a first perfluoroalkylvinyl ether and at least one first cure site monomer having a cure site,wherein a molar ratio of the tetrafluoroethylene to the firstperfluoroalkyl vinyl ether is about 0:100 to about 65:35 in theperfluoropolymer; (ii) a second curable perfluoropolymer comprisingtetrafluoroethylene, a second perfluoroalkylvinyl ether which may be thesame or different from the first perfluoroalkylvinyl ether, and at leastone second cure site monomer having a cure site which may be the same ordifferent from the at least one first cure site monomer, wherein a molarratio of the tetrafluoroethylene to the second perfluoroalkylvinyl etheris about 65:35 to about 95:5 in the polymer; and (iii) at least onecurative capable of curing the cure site of the at least one first curesite monomer and the cure site of the at least one second cure sitemonomer; and (b) curing the first and second curable perfluoropolymersin the perfluoroelastomeric composition to form a curedperfluoroelastomeric composition. Such molded articles herein may besealing members that can be bonded to a surface comprising a metal or ametal alloy such as to a surface of a door for sealing a semiconductorprocessing chamber or other reaction chamber.

DETAILED DESCRIPTION OF THE INVENTION

New perfluoroelastomer compositions, and/or molded articles madetherefrom such as sealing members including O-rings, seals, gaskets andthe like as described herein provide required chemical and plasmaresistance, and more particularly provide excellent levels ofhigh-temperature resistance and plasma resistance for such moldedarticles, particularly when exposed to remote NF₃ plasma. Moldedarticles made in accordance with the curable and cured compositionsherein have the characteristics suitable for use in semiconductor plasmaand gas chemical vapor deposition (CVD) applications including highdensity plasma CVD (HDPCVD), plasma-enhanced CVD (PECVD) and atomiclayer deposition (ALD) and plasma-enhanced atomic layer deposition(PEALD). From processing and performance perspectives, the curable andcured compositions described herein provide articles that performequivalent to or better than various prior art filled FFKM compositionswhich incorporate semicrystalline fluoroplastics as particulate fillersas described in the Background hereof.

The perfluoroelastomer compositions may have two or more types ofperfluoroelastomers, least two of which, have varyingperfluoroalkylvinyl ether (PAVE) monomer content. The difference incontent, measured in percent by mole, between any two such differingPAVE-content perfluoroelastomers in the compositions is preferably fromabout 5% to about 25%.

In addition, compositions herein are directed to achieving shorterperfluoroelastomer crosslinking times when using a perfluoroelastomer inthe composition, which has a generally lower content of PAVE than, isnormally used in such compositions.

As used in this application, “perfluoroelastomer” or “curedperfluoroelastomer” unless otherwise indicated, includes any curedelastomeric material or composition that is formed by curing a curableperfluoropolymer(s) such as the curable perfluoropolymers in the curableperfluoroelastomeric compositions described herein. A “curableperfluoropolymer” (sometimes referred to in the art as a“perfluoroelastomer” or more appropriately a “perfluoroelastomer gum”)that may be used to form a cured perfluoroelastomer is a polymer that issubstantially completely fluorinated, which is preferably completelyperfluorinated on its polymeric backbone. It will be understood, basedon this disclosure, that some residual hydrogen may be present in someperfluoroelastomers within the crosslinks of those materials due to useof hydrogen as part of a functional crosslinking group. Cured materials,such as perfluoroelastomers are generally cross-linked polymericstructures.

The curable perfluoropolymers that are used in perfluoroelastomericcompositions to form cured perfluoroelastomers upon cure are formed bypolymerizing one or more perfluorinated monomers, one of which ispreferably a perfluorinated cure site monomer having a functional groupto permit curing, wherein the functional group includes a reactive groupthat may not be perfluorinated. Two or more perfluoropolymers, andpreferably at least one curing agent, are combined in aperfluoroelastomeric composition that is then cured forming theresulting crosslinked, cured perfluoroelastomeric compositions asdescribed herein.

As used herein, a “perfluoroelastomeric composition” is a polymericcomposition including one or more, and preferably more than one curableperfluoropolymers, each of which is formed by polymerizing two or moreperfluorinated monomers, including at least one perfluorinated monomerwhich has at least one functional group to permit curing, i.e. at leastone cure site monomer. Such materials are also referred to generally asFFKMs in accordance with the American Standardized Testing Methods(ASTM) standardized rubber definitions and as described further herein.

As used herein, “compression set” refers to the propensity of anelastomeric material to remain distorted and not return to its originalshape after a deforming compressive load has been removed. Thecompression set value is expressed as a percentage of the originaldeflection that the material fails to recover. For example, acompression set value of 0% indicates that a material completely returnsto its original shape after removal of a deforming compressive load.Conversely, a compression set value of 100% indicates that a materialdoes not recover at all from an applied deforming compressive load. Acompression set value of 30% signifies that 70% of the originaldeflection has been recovered. Higher compression set values generallyindicate a potential for seal leakage and so compression set values of30% or less are preferred in the sealing arts.

As described herein, the invention includes a preferred curableperfluoroelastomeric composition, cured perfluoroelastomer compositionsand molded articles formed from the same.

Such perfluoroelastomeric compositions preferably include two or moreperfluorinated copolymers, at least one of which perfluorinatedcopolymers has a higher content of tetrafluoroethylene (TFE) than asecond polymer in the composition. Other suitable co-monomers mayinclude other ethylenically unsaturated fluoromonomers. Each suchpolymer also has one or more perfluoroalkylvinyl ethers (PAVEs), whichinclude alkyl or alkoxy groups that may be straight or branched andwhich may also include ether linkages, wherein preferred PAVEs for useherein include, for example, perfluoromethylvinyl ether (PMVE),perfluoroethylvinyl ether (PEVE), perfluoropropylvinyl ether (PPVE),perfluoromethoxyvinyl ether and other similar compounds, with especiallypreferred PAVEs being PMVE, PEVE and PPVE, and most preferred being PMVEwhich provides excellent mechanical strength to resulting articlesformed from curing the curable compositions herein. The PAVEs may beused alone or in combinations of the above-noted PAVE types within thecurable perfluoropolymers and in the ultimate curable compositions solong as the use is consistent with the invention as described herein.

Preferred perfluoropolymers are co-polymers of TFE, at least one PAVE,and at least one perfluorinated cure site monomer that incorporates afunctional group to permit crosslinking of the curable polymer. The curesite monomers may be of a variety of types with preferred cure sitesnoted herein. While preferred cure sites include those having anitrogen-containing group, a carboxyl group or an alkylcarbonyl group,other cure sites such as iodine, bromine and other halogenated cures aswell as other cure sites known in the art may also be used, particularlyif additional curable perfluoropolymers beyond the first and secondcurable perfluoropolymers are provided to the composition. Consequently,while the disclosure herein provides a variety of preferred curatives(also referred to herein as crosslinking agents, curing agents), ifother cure sites known in the art are used, other curatives that arecapable of curing such alternative cure sites may also be used. Forexample, organic peroxide-based curatives and co-curatives may be usedwith halogenated functional cure site groups.

Exemplary cure site monomers are listed below, most of which arePAVE-based in structure and have a reactive site, although they mayvary, are those having the following structure (A):

CF₂═CFO(CF₂CF(CF₃)O)_(m)(CF₂)_(n)—X¹  (A)

wherein m is 0 or an integer from 1 to 5, n is an integer from 1 to 3and X¹ is a nitrogen-containing group, such as nitrile or cyano, acarboxyl group and/or an alkoxycarbonyl group. The functional groupsnoted herein, such as the nitrogen-containing groups, are the sites forcrosslinking. Compounds according to formula (A) may be used alone or invarious, optional, combinations thereof. From a crosslinkingperspective, it is preferred that the crosslinking functional group is anitrogen-containing group, preferably a nitrile group.

Further examples of cure site monomers according to formula (A) includeformulas (1) through (17) below:

CY₂═CY(CF₂)_(n)—X²  (1)

wherein Y is H or F, n is an integer from 1 to about 8

CF₂═CFCF₂R_(f) ²—X²  (2)

wherein R_(f) ² is (—CF₂)_(n)—, —(OCF₂)_(n)— and n is 0 or an integerfrom 1 to about 5

CF₂═CFCF₂(OCF(CF₃)CF₂)_(m)(OCH₂CF₂CF₂)_(n)OCH₂CF₂—X²  (3)

wherein m is 0 or an integer from 1 to about 5 and n is 0 or an integerof from 1 to about 5

CF₂═CFCF₂(OCH₂CF₂CF₂)_(m)(OCF(CF₃)CF₂)_(n)OCF(CF₂)—X²  (4)

wherein m is 0 or an integer from 1 to about 5, and n is 0 or an integerof from 1 to about 5

CF₂═CF(OCF₂CF(CF₃))_(m)O(CF₂)_(n)—X²  (5)

wherein m is 0 or an integer from 1 to about 5, and n is an integer offrom 1 to about 8

CF₂═CF(OCF₂CF(CF₃))_(m)—X²  (6)

wherein m is an integer from 1 to about 5

CF₂═CFOCF₂(CF(CF₃)OCF₂)_(n)CF(—X²)CF₃  (7)

wherein n is an integer from 1 to about 4

CF₂═CFO(CF₂)_(n)OCF(CF₃)—X²  (8)

wherein n is an integer of from 2 to about 5

CF₂═CFO(CF₂)_(n)—(C₆H₄)—X²  (9)

wherein n is an integer from 1 to about 6

CF₂═CF(OCF₂CF(CF₃))_(n)OCF₂CF(CF₃)—X²  (10)

wherein n is an integer from 1 to about 2

CH₂═CFCF₂O(CF(CF₃)CF₂O)_(n)CF(CF₃)—X²  (11)

wherein n is 0 or an integer from 1 to about 5

CF₂═CFO(CF₂CF(CF₃)O)_(m)(CF₂)_(n)═X²  (12)

wherein m is 0 or an integer from 1 to about 4 and n is an integer of 1to about 3

CH₂═CFCF₂OCF(CF₃)OCF(CF₃)—X²  (13)

CH₂═CFCF₂OCH₂CF₂—X²  (14)

CF₂═CFO(CF₂CF(CF₃)O)_(m)CF₂CF(CF₃)—X²  (15)

wherein m is an integer greater than 0

CF₂═CFOCF(CF₃)CF₂O(CF₂)_(n)—X²  (16)

wherein n is an integer that is at least 1

CF₂═CFOCF₂OCF₂CF(CF₃))OCF₂—X²  (17)

wherein X² can be a monomer reactive site subunit such as a nitrile(—CN), carboxyl (—COOH), or an alkoxycarbonyl group (—COOR⁵, wherein R⁵is an alkyl group of 1 to about 10 carbon atoms which may be fluorinatedor perfluorinated), and the like. It is preferred that perfluorinatedcompounds having no hydrogen atoms are used if excellent heat resistanceis desired for the perfluoroelastomer resulting from curing theperfluoropolymers as well as for preventing decrease in molecular weightdue to chain transfer when synthesizing the perfluoroelastomer bypolymerization reaction. Further, compounds having a CF₂═CFO— structureare preferred from the viewpoint of providing excellent polymerizationreactivity with TFE.

Suitable cure site monomers preferably include those havingnitrogen-containing cure sites such as nitrile or cyano cure sites, forpreferred crosslinking reactivity. However, cure sites (having multipleand varied backbones in addition to those noted above) and havingcarboxyl, COOH and other similar cure sites known in the art and to bedeveloped may also be used. The cure site monomers may be used alone orin varied combinations.

Examples of perfluoropolymers and resulting elastomers formed therefromusing cure site monomers such as those noted above may be found in WO00/29479 A1, incorporated herein in relevant part with respect to suchperfluoroelastomers, their content and methods of making the same.Reference is also made to Japanese Kokai Patents No. H09-512569 A andH11-092529 A.

Perfluoropolymers for use in the compositions claimed herein may besynthesized using any known or to be developed polymerization techniquefor forming fluorine-containing elastomers using polymerization,including, for example, emulsion polymerization, latex polymerization,chain initiated polymerization, batch polymerization and others.Preferably, the polymerization is undertaken so that reactive cure sitesare located either on either or both terminal ends of the polymerbackbone and/or are depending from the main polymer backbone.

One possible method of making the polymers includes radicalpolymerization using an initiator such as those known in the art forpolymerization of fluorine-containing elastomers (organic or inorganicperoxide and azo compounds). Typical initiators are persulfates,percarbonates, peresters and the like, with preferred initiators beinginclude salts of persulfuric acid, oxidizing carbonates and esters, andammonium persulfate, with the most preferred being ammonium persulfate(APS). These initiators may be used alone or with reducing agents, suchas sulfites and sulfite salts.

A wide variety of emulsifiers for emulsion polymerization can be used,but preferred are salts of carboxylic acid having a fluorocarbon chainor a fluoropolyether chain, to suppress chain transfer reactions to theemulsifier molecules that occur during polymerization. The amount ofemulsifier is generally used in amounts of about 0.05 to 2 weightpercent, and preferably 0.2 to 1.5 weight percent, based on the addedwater. It is noted that a special arrangements should be used to avoidan ignition source, such as sparks, near the polymerization equipment.See, G. H. Kalb, Advanced Chemistry Series, 129, 12 (1973).

Polymerization pressure may vary, and can generally be in the range 0.5to 7 MPa. The higher the polymerization pressure is, the higher thepolymerization rate will be. Accordingly if productivity enhancement isdesired, the polymerization pressure is preferably at least 0.7 MPa.

Standard polymerization procedures known in the art may be used. If anitrogen-containing group, such as nitrile or cyano, a carboxyl group,or an alkoxycarbonyl group is to used in the curable perfluoropolymersherein, it may be included in the polymer by copolymerizing anadditional monomer having the crosslinking site containing that group.The cure-site monomer may be added and copolymerized when preparing thefluorine-containing elastomer. A further method for providing such agroup to the polymer is by subjecting a polymerization product to anacid treatment to convert a group such as a metallic salt or ammoniumsalt of a carboxylic acid contained in the polymerization product to acarboxyl group. Examples of a suitable acid treatment method are washingwith hydrochloric acid, sulfuric acid, nitric acid or fuming sulfuricacid or by decreasing a pH value of a mixture system after thepolymerization reaction to 3 or less by using the above-mentioned acids.Another method for introducing a carboxyl group is by oxidizing acrosslinkable polymer having iodine and bromine, with fuming nitricacid.

Uncured perfluoropolymers are commercially available, includingperfluoropolymers sold by Dyneon, Daiel-Perfluor® and other similarpolymers, available from Daikin Industries, Ltd. of Osaka, Japan. Othersuitable materials are available also from Ausimont S.p.A. in Italy,Asahi Glass, Japan, and W.L. Gore.

Curing agents (also referred to herein as crosslinking agents) for usewith various perfluoroelastomer compositions and elastomer-containingcompositions of the present invention are for use with various curesites described herein and should be capable of curing (crosslinkableto) the cure site in the various uncured perfluoropolymers in thecompositions. Preferred crosslinking or curing agents are oxazole,imidazole, thiazole, triazine, amidoxime, and amidrazone crosslinkingagents. Of these, imidazole is preferred in that crosslinked articleproviding excellent mechanical strength, heat resistance, chemicalresistance, cold resistance is achievable, particularly a cured articlewhich is balanced and excellent with respect to heat resistance and coldresistance.

For preferred nitrogen-containing cure sites include bisphenyl-basedcuratives and derivatives thereof, including bisaminophenol and itssalts, and tetraphenyltin. In addition, the perfluoropolymers may becured using radiation-curing technology.

Most preferred are cyano-group containing cure sites cured withcuratives that are aromatic amines having at least two crosslinkablegroups as in formulas (I) and (II) below, or a combination thereof,which form benzoimidazole cross-linking structures upon cure. Thesecuratives are known in the art and discussed in relevant part and withspecific examples in U.S. Pat. No. 6,878,778 and U.S. Pat. No.6,855,774, which are incorporated herein in their entirety.

wherein R¹ is the same or different in each group according to formula(II) and may be NH₂, NHR², OH, SH or a monovalent organic group or otherorganic group such as alkyl, alkoxy, aryl, aryloxy, aralkyl andaralkyloxy of from about 1 to about 10 carbon atoms, wherein thenon-aryl type groups may be branched or straight chain and substitutedor unsubstituted and R² may be —NH₂, —OH, —SH or a monovalent or otherorganic group such as an aliphatic hydrocarbon group, a phenyl group anda benzyl group, or alkyl, alkoxy, aryl, aryloxy, aralkyl and aralkyloxygroups, wherein each group is from about 1 to about 10 carbon atoms,wherein the non-aryl type groups may be branched or straight chain andsubstituted or unsubstituted. Preferred monovalent or other organicgroups, such as alkyl and alkoxy (or perfluorinated versions thereof)are from 1 to 6 carbon atoms, and preferred aryl type groups are phenyland benzyl groups. Examples thereof include —CF₃, —C₂F₅, —CH₂F, —CH₂CF₃or —CH₂C₂F₅, a phenyl group, a benzyl group; or a phenyl or benzyl groupwherein 1 to about 5 of the hydrogen atoms are substituted by fluorineatoms such as —C₆F₅, —CH₂C₆CF₅, wherein groups may be furthersubstituted, including with —CF₃ or other lower perfluoroalkyl groups,or, phenyl or benzyl groups in which 1 to 5 hydrogen atoms aresubstituted by CF₃ such as for example C₆H_(5-n)(CF₃)_(n),—CH₂C₆H_(5-n)(CF₃)_(n) (wherein n is from 1 to about 5). Hydrogen atomsmay be further substituted with phenyl or benzyl groups. However, aphenyl group and CH₃ are preferred as providing superior heatresistance, good cross-linking reactivity and relatively easy synthesis.

A structure having formula (I) or (II) incorporated in an organic amineshould include at least two such groups of formula (I) or (II) such thatat least two cross-linking reactive groups are provided.

Also useful herein are curatives having formulas (III), (IV) and (V)shown below.

wherein R³ is preferably SO, O or CO or an organic or alkylene typegroup, such as an alkyl, alkoxy, aryl, aralkyl or aralkoxy group of fromone to six carbon atoms or perfluorinated versions of such groups,having from about one to about 10 carbon atoms, and being branched orstraight chain, saturated or unsaturated, and branched or straight chain(with respect to the non-aryl type groups) or a single bond. R⁴ ispreferably a reactive side group such as those set forth below:

wherein R_(f) ¹ is a perfluoroalkyl or perfluoroalkoxy group of fromabout 1 to about 10 carbon atoms that may be a straight or branchedchain group and/or saturated or unsaturated and/or substituted orunsubstituted; and

wherein n is an integer of about 1 to about 10.

With respect to heat resistance, oxazole, imidazole, thiazole andtriazine crosslinking agents are preferred and can include the formulacompounds listed below and discussed further below with respect toFormulae (I), (II), (III), (IV) and (V), specifically, formula (II)wherein R² is the same or different and each is —NH₂, —NHR², —OH or —SH,wherein R² is a monovalent organic group, preferably not hydrogen;formula (III) wherein R³ is —SO₂—, —O—, —CO—, and alkylene group of 1 toabout 6 carbon atoms, a perfluoroalkylene group of 1 to about 10 carbonatoms or a single bond and R⁴ is as noted below; formula (IV) whereinR_(f) ¹ is a perfluoroalkylene group of 1 to about 10 carbon atoms, andformula (V) wherein n is an integer of 1 to about 10. Of such compounds,those of formula (II) as noted herein are preferred for heat resistance,which is enhanced due to stabilization of the aromatic rings aftercrosslinking. With respect to R¹ in the formula (II), it is preferredalso to use —NHR² as R¹, since an N—R² bond (wherein R² is a monovalentorganic group and not hydrogen) is higher in oxidation resistance thanan N—H bond,

Compounds having at least two groups as in formula (II) are preferredand having 2 to 3 crosslinkable reactive groups thereon, more preferablyhaving 2 crosslinkable groups.

Exemplary curatives based on the above preferred formulae include atleast two functional groups, such as the following structures formula(VI), (VII) or (VIII):

wherein R⁵ represents a saturated or unsaturated, branched or straightchain, substituted or unsubstituted group such as alkyl, alkoxy, aryl,SO, O, CO, or similar groups which are perfluorinated with respect tothe carbon atoms and which is preferably about 1 to about 10 carbonatoms;

wherein R¹ is as defined elsewhere herein and R⁶ may be O, SO₂, CO or anorganic group which may be perfluorinated, such as alkyl, alkoxy, aryl,aryloxy, aralkyl and aralkyloxy of from about 1 to about 10 carbonatoms, wherein the non-aryl type groups may be branched or straightchain and substituted or unsubstituted, or a single or alkylene bond.

From the view of easy synthesis, preferred crosslinking agents arecompounds having two crosslinkable reactive groups as represented byformula (II) are shown below in formula (VIII).

wherein R¹ is as above and R⁶ is —SO₂, —O—, —CO—, an alkylene group of 1to about 6 carbon atoms, a perfluoroalkylene group of 1 to about 10carbon atoms, a single bond or a group as shown in Formula (IX):

wherein this formula provides an easier the synthesis. Preferredexamples of alkylene groups of from 1 to about 6 carbon atoms aremethylene, ethylene, propylene, butylene, pentylene, hexylene and thelike. Examples of perfluoroalkylene groups of 1 to about 10 carbon atomsare

and the like. These compounds are known as examples of bisaminophenylcompounds. See, as a reference for example, the compounds in JapanesePatent No. 2-591177 B and Japanese Kokai Application No. 8-120146 A andsimilar patents. Preferred compounds according to this structure includethose of formula (X):

wherein R⁷ is the same or different in each instance and each R⁷ ishydrogen, an alkyl group of 1 to about 10 carbon atoms; a partiallyfluorinated or perfluorinated alkyl group of 1 to 10 carbon atoms; aphenyl group; a benzyl group; or a phenyl or benzyl group in which 1 toabout 5 hydrogen atoms have been replaced by fluorine or a lower alkylor perfluoroalkyl group such as CF₃.

Non-limited examples of curatives include2,2-bis(2,4-diaminophenylhexafluoropropane,2,2-bis[3-amino-4-(N-methylamino)phenyl]hexafluoropropane,2,2-bis[3-amino-4-(N-ethylamino)phenyl]hexafluoropropane,2,2-bis[3-amino-4-(N-propylamino)phenyl]hexafluoropropane,2,2-bis[3-amino-4-(N-phenylamino)phenyl]hexafluoropropane,2,2-bis[3-amino-4-(N-perfluorophenylamino)phenyl]hexafluoropropane,2,2-bis[3-amino-4(N-benzylamino)phenyl]hexafluoropropane, and similarcompounds. Of these, for preferred excellent heat resistance properties,2,2-bis[3-amino-4(N-methylamino)phenyl]hexafluoropropane,2,2-bis[3-amino-4-(N-ethylamino)phenyl]hexafluoropropane,2,2-bis[3-amino-4-(N-propylamino)phenyl]hexafluoropropane and2,2-bis[3-amino-4-(N-phenylamino)phenyl]hexafluoropropane are preferred.For most preferred excellent heat resistant properties,2,2-bis[3-amino-4-(N-phenylaminophenyl)]hexafluoropropane is preferred.

Other suitable curatives include oxazole, imidazole, thiazole, triazine,amidoxime and amidrazone crosslinking agents, and particularlybisaminophenols, bisamidines, bisamidoximes, bisamidrazones,monoamidines, monoamidoximes and monoamidrazones as known in the art orto be developed, examples of which are set forth, for example in U.S.Patent Publication No. 2004/0214956 A1, incorporated herein in relevantpart by reference, including the curatives and co-curatives andaccelerators therein. Imidazoles are useful in that they can providegood mechanical strength, heat resistance, chemical resistance, and lowtemperature capacity, as well as a good balance of crosslinkingproperties and high and low temperature properties. The bisamidoxime,bisamidrazone, bisaminophenol, bisaminothiophenol or bisdiaminophenylcuratives can react with nitrile or cyano groups, carboxyl groups,and/or alkoxycarbonyl groups in the perfluoropolymer to preferably forma perfluoroelastomer having an oxazole ring, a thiazole ring, animidazole ring, or a triazine ring as crosslinks in the resulting curedarticles formed from the compositions herein.

It is preferred to have a compound including at least two chemicalgroups with cross-linking reactive groups as in Formula (I) or (II) inorder to increase heat resistance and to stabilize an aromatic ringsystem. For groups such as in (I) or (II), having two to three suchgroups, it is preferred to have at least two in each group (I) or (II),as having a lesser number of groups may not provide adequatecross-linking.

In one embodiment, the curable perfluoroelastomeric composition includesat least two curable perfluoropolymers, a first perfluoropolymer and asecond perfluoropolymer, which have differing PAVE content, however, itshould be understood that additional such perfluoroelastomers may becombined with the first and the second perfluoropolymers, and also havevarying amounts of PAVE, provided at least the first and the secondperfluoropolymers (and in cured compositions the first and secondperfluoroelastomers) have varying PAVE content as discussed herein. Itis preferred to use a high-PAVE content curable perfluoropolymer and alow-PAVE content curable perfluoropolymer, alone or in a combinationwith one or more additional curable perfluoropolymers as use of twoPAVEs, which are both low-PAVE content polymers, while beneficial insome ways, contributes to decreasing crosslinking time. However, thebetter the PAVE differential approaching the optimum ranges describedherein, the better and the shorter the crosslinking time will be. Suchpreferred differential PAVE content also contributes to the easyadjustment of hardness in end products, such as molded articles, formedfrom the fluorine-containing elastomer compositions.

The first curable perfluoropolymer preferably includestetrafluoroethylene in an amount of about 0 to about 58.5 mole percent,and preferably 49.8 to about 63.1 mole percent. A firstperfluoroalkylvinyl ether (which may include at least oneperfluoroalkylvinyl ether which can be used alone or in combination withother perfluoroalkylvinyl ethers), and at least one first cure sitemonomer having a cure site. The perfluoroalkylvinyl ether is preferablypresent in the first curable perfluoropolymer in an amount of 31.5 toabout 99.99, and preferably about 34 to about 49.75 mole percentage ofthe perfluoropolymer or about 38 to about 50 mole percent of thepolymer. In one embodiment, in a fluorine-containing elastomercomposition, the first perfluoropolymer is the high PAVE-content curableperfluoropolymer and the content of PAVE therein is preferably at leastabout 38% by mole, and more preferably at least about 40% by mole toenhance crosslinking speed of the composition. Corresponding in thisembodiment, the PAVE content is preferably no greater than about 50% bymole, more preferably no greater than about 45% by mole and mostpreferably no greater than bout 42% by mole so as to increase thepolymerization rate in synthesizing the polymer.

Most preferably, the first curable perfluoropolymer has a molarpercentage ratio of tetrafluoroethylene to the first perfluoroalkylvinylether(s) in the polymer chain of about 0:100 to about 65:35, and morepreferably from about 50:50 to about 65:35.

The at least one first cure site monomer having a cure site ispreferably a single cure site monomer, but combinations of cure sitemonomers having the same functional active cure group or varying typesof cure site monomers having differing cure site groups (as in a dualcure composition) may also be used herein.

The second curable perfluoropolymer preferably includes a higher contentof tetrafluoroethylene than the first curable perfluoropolymer, and morepreferably about 65 to about 85.5 mole percentage oftetrafluoroethylene, and most preferably about 64.7 to about 82.5 molepercent in the second curable polymer. The second perfluoroalkylvinylether in the second curable perfluoropolymer, which is the low-PAVEcontent perfluoropolymer may also be one or more perfluoroalkylvinylethers used alone or in combination, and the second perfluoroalkylvinylether(s) may be the same or different from the first perfluoroalkylvinylether(s) in the first curable perfluoropolymer. The secondperfluoroalkylvinyl ether is preferably present at about 4.5 to about 35mole percent, and more preferably about 14.6 to about 34.83 mole percentof the second perfluoropolymer.

In one embodiment, in a fluorine-containing elastomer composition, thesecond curable PAVE is present in the polymer preferably in an amount ofat least about 18% by mole, more preferably at least about 21% by moleand most preferably at least about 25% by mole, so as to contribute to alower glass transition temperature and satisfactory low temperatureproperties. In that embodiment, the PAVE content is also preferably nogreater than about 35% by mole, and more preferably no greater thanabout 32% by mole and most preferably no greater than about 30% by moleso as to contribute to an increase in hardness of resulting crosslinkedarticles formed from curing the fluorine-containing elastomercomposition and for enhancing sealing properties of such articles.

Most preferably, the second curable perfluoropolymer has a molarpercentage ratio in the polymer chain of tetrafluoroethylene to thesecond perfluoroalkylvinyl ether(s) of about 65:35 to about 95:5, andmore preferably about 65:35 to about 85:15.

It is most preferred that the difference in PAVE content in the firstcurable perfluoropolymer and the second curable perfluoropolymer is atleast 5 molar percent to provide adjustment of hardening of thecrosslink. It is preferred, however, that the difference in the PAVEcontent between the first and second curable perfluoropolymers be atleast about 8 molar percent, and more preferred that it is at leastabout 10 molar percent. It is further preferred that he difference incontent in PAVE content is less than about 25 molar percent, morepreferably less than about 15 molar percent and most preferably lessthan about 10 molar percent to avoid increases in the glass transitionpoint.

The second curable perfluoropolymer preferably also comprises at leastone second cure site monomer having a cure site. The second cure sitemonomer(s) may be the same or different from the at least one first curesite monomer(s) used in the first curable perfluoropolymer, although itis preferred that the first and second cure site monomer(s) are eitherof the same type (meaning that they are the same or have the same curesite functional group(s)) or are capable of being cured by the samecurative for convenience and compatibility. Although it should beunderstood by those skilled in the art, based on this disclosure thatdual cure materials may be used, or varying cures between the first andsecond curable polymers within the scope of the invention, provided thatpreferably adequate curing is obtained through use of the appropriatecuratives.

In both the first curable perfluoropolymer and second perfluoropolymer,the polymers preferably include the cure site monomer(s) in amounts ofabout 0.01 to about 10 molar percentage of the polymer chains, and morepreferably about 0.05 to about 3 molar percent. While various cure sitefunctional groups may be used within the scope of the invention, it ispreferred that the cure sites of the at least one first and at least onesecond cure site monomers each is a functional group that is anitrogen-containing group such as nitrile, a carboxyl group or analkoxycarbonyl group. The monomers may be configured so that the firstand/or the second cure site monomer(s) provide a functional group suchas a nitrogen-containing group on one or two of the terminal ends of thefirst or second curable perfluoropolymer, respectively. Alternatively,or in additional to terminal end placement of groups, such cure sitegroups having nitrogen may also be situated so as to depend from thepolymer backbone of either the first and/or the second curableperfluoropolymer.

In one preferred embodiment, in a fluorine-containing elastomercomposition, the content of the at least one cure site monomer is atleast about 0.1% by mole, more preferably at least about 0.2% by moleand most preferably at least about 0.3% by mole in order to provideenhanced crosslinkability. Further, in such embodiment, the at least onecure site monomer is no greater than about 2.0% by mole, more preferablyno greater than about 1.0% by mole and most preferably no greater thanabout 0.5% by mole to avoid use of excessive cure site monomer due toexpense associated therewith.

The curable perfluoropolymer compositions described herein arepreferably a combination of two curable perfluoropolymers, but theinvention may also include within its scope the addition of further suchcurable perfluoropolymers without departing from the spirit of theinvention.

In addition to the curable perfluoropolymers described above, thecurable perfluoroelastomer composition preferably also includes at leastone curative(s) which is/are capable of curing the at least one firstcure site monomer and the at least one second cure site monomer.Preferably, if a functional-group containing cure site is used in thefirst and/or the second curable perfluoropolymer, the at least onecurative is selected so as to react with the functional group(s) of thecure site monomer(s) in order to form cross-linking structures such asbenzoimidazole cross-linking structures. Suitable curatives are as notedelsewhere herein and are included in the curable perfluoroelastomericcomposition in amounts of about 0.3 to about 10 parts by weight perhundred parts of the curable composition based on the total weight ofthe first and the second curable perfluoropolymers (or total curableperfluoropolymers), and more preferably about 0.6 to about 0.9 parts byweight per hundred parts of the curable perfluoroelastomeric compositionthereof. The preferred range is most beneficial to provide good strengthcharacteristics and to avoid cracking or structural defects when underhigh-temperature compression forces. It also provides preferredcompression set characteristics.

In one embodiment of the fluorine-containing elastomers herein, thecurative is one of those listed as preferred above, and is present in anamount by weight of at least about 0.3 parts by weight, and morepreferably at least about 0.5 parts by weight or at least about 0.7parts by weight, and most preferably at least about 0.6 parts by weightbased on 100 parts by weight of elastomer in the composition, withgreater amounts enhancing crosslinking. The curative or crosslinkingagent is preferably no greater than 10.0 parts by weight, and morepreferably no greater than 2.0 parts by weight and most preferably nogreater than 0.9 parts by weight based on 100 parts by weight of theelastomers in the composition.

In addition to the preferred curatives noted herein for use withfluorine-containing curable perfluoropolymers having nitrile groups andthe like, it is within the scope of the invention to cure the nitrilegroups using curatives known in the art for the first and secondperfluoropolymers and/or for other perfluoropolymers added to thecompositions herein. Examples of other curatives known in the artinclude organotins such as tetraphenyltin, triphenyltin and the like (asthese compounds form preferred triazine rings). If an organotin compoundis used, it is preferred to be present in an amount of about 0.05 toabout 10 parts by weight, more preferably about 1 to about 5 parts byweight, based on 100 parts by weight of the curable perfluoropolymers inthe composition. If the organotin is present in an amount of less thanabout 0.05 parts, there is a tendency for the polymer to notsufficiently crosslink upon curing and if the amount is more than about10 parts, physical properties of the formed articles tend todeteriorate.

In addition to the above-described curable perfluoroelastomericcomposition, described herein are cured perfluoroelastomeric compositionincludes at least a first cured perfluoroelastomer and a second curedperfluoroelastomers, which cured elastomers are formed from the at leasttwo, and preferably only two of the above-described curableperfluoropolymers in the composition after the cure is complete suchthat the curative(s) in the curable perfluoroelastomeric compositionhas/have been substantially reacted and incorporated into thecross-linked cured perfluoroelastomeric composition.

It is within the scope of the invention to combine these curablematerials in varying amounts so that the weight percentage ratio of thefirst perfluoroelastomer to the second perfluoroelastomer in thecomposition is about 1:99 to about 99:1, more preferably about 20:80 toabout 80:20, and most preferably about 75:25 to about 45:55.

Such cured perfluoroelastomer compositions formed from curableperfluoroelastomeric compositions as noted herein may be cured andshaped so as to form a molded article(s). Generally, the molded articleswill be formed as sealing members such as O-rings, seals, gaskets,inserts and the like, but other shapes and uses known or to be developedin the art are contemplated herein.

The molded article may be bonded to a surface for forming, for example,bonded seals. Such bonded seals may be used, for example for formingpre-bonded doors, gates, and slit valve doors for use, e.g., insemiconductor processing. The surfaces to which such molded articles,such as seals may be bonded include polymeric surfaces as well as metaland metal alloy surfaces. In one embodiment, the invention includes agate or slit valve door formed of, e.g., stainless steel or aluminum, towhich an O-ring seal conforming to a recess in the door configured forreceiving the seal. The bonding may occur through use of a bondingcomposition or through an adhesive. Further, a bonding agent may beprepared which is formed of a fluorosolvent, such as one of severalFluorinert® solvents from 3M capable of dissolving a perfluoropolymer,at least one curable perfluoropolymer and a curative.

The bonding agent may be applied to the O-ring or the recess of the dooreither after initial curing of an extruded polymer in a mold for makingan O-ring and prior to bonding the seal to a surface such as a door, orthe bonding agent can be applied to an extruded polymer which can bemolded and cured in situ in the surface (door) to which it is to bebonded so that upon heat curing, the perfluoropolymers are cured in theO-ring and also within the bonding agent at the same time. Preferably,although not necessarily, the perfluoropolymer used in the bonding agentis the same as at least one of the perfluoropolymers in theperfluoroelastomer compositions described herein. The bonding agent mayalso preferably include both perfluoropolymers used in the curableperfluoroelastomeric compositions described herein and/or can be usefulusing any suitable curable perfluoropolymer capable of curing to bondthe compositions to the intended surface.

Also described herein is a method for making a curedperfluoroelastomeric composition as described hereinabove. In themethod, a curable perfluoroelastomeric composition is prepared bycombining at least two curable perfluoropolymers as described elsewhereherein as a first and a second perfluoropolymer and at least onecurative capable of curing the cure site of the at least one first andsecond cure site monomer(s).

The polymers may be combined using typical rubber processing equipmentsuch as an open roll, Banbury mixer, kneader or the like. Thecompositions may also be prepared using a method of a closed mixer and amethod of coagulation through emulsion mixing. Preferably a typicalmixer, such as a two-roll mixer as is typically used for combiningperfluoropolymers (also referred to as perfluoroelastomer gum).Preferably, in this method, the polymers are mixed at room temperatures,or at elevated temperatures of about 30° C. to about 100° C., andpreferably about 50° C.

If desired, additives may also be admixed into the composition at thispoint. Additives are optional and not required due to the unique natureof the interaction of the first and second curable perfluoropolymers.However, if desired to alter certain properties, cure accelerators,co-curatives, co-agents, processing aids, plasticizers, fillers andmodifiers such as silica, fluoropolymers (TFE and its melt-processiblecopolymers as well as core-shell modified fluoropolymers as are known inthe art in micropowder, pellet, fiber and nanopowder forms),fluorographite, silica, barium sulfate, carbon, carbon black, carbonfluoride, clay, talc, metallic fillers (titanium oxide, aluminum oxide,yttrium oxide, silicon oxide), metal carbides (silicon carbide, aluminumcarbide), metallic nitrides (silicon nitride, aluminum nitride), otherinorganic fillers (aluminum fluoride, carbon fluoride), colorants,organic dyes and/or pigments, such as azo, isoindolenone, quinacridone,diketopyrrolopyrrole, anthraquinone, and the like, imide fillers (suchas polyimide, polyamide-imide and polyetherimide), ketone plastics (suchas polyarylene ketones like PEEK, PEK and PEKK), polyarylates,polysulfones, polyethersulfones, polyphenylene sulfides,polyoxybenzoate, and the like may be used in amounts known in the artand/or which may be varied for different properties. All of the fillersherein may be used alone or in combinations of two or more such fillersand additives.

Preferably, any optional fillers used total less than about 30 parts perhundred parts of the combined curable perfluoropolymers in thecomposition: Organic fillers, providing heat resistance, and plasmaresistance (reduced numbers of particles and low weight reduction ratesat emission of plasma), include of those mentioned above, organicpigments, imide fillers with imide structures such as polyimide,polyamide imide and polyetherimide, and ketone-based engineeringplastics like PEEK, and PEK, with organic pigments being preferred.

Pigmented fillers which are preferred for heat resistance and chemicalresistance and having less effect on end characteristics of the moldedarticles formed from the compositions described herein includequinacridone, diketopyrrolopyrrole and anthraquinone pigments and dyes,with quinacridone being preferred.

Of the inorganic fillers, preferred fillers for shielding plasma effectsinclude aluminum oxide, yttrium oxide, silicon oxide, polyimide andcarbon fluoride.

After the polymers are combined, the first and second curableperfluoropolymers in the perfluoroelastomeric composition are cured toform a cured perfluoroelastomeric composition as described herein.

Depending on the cure sites and curative, various cross-link structurescan be formed upon curing. Preferably, functional cure groups are usedon the cure site monomers, so that the cured perfluoroelastomericcomposition includes a curative(s) which form benzoimidazolecross-linking structures.

The curable perfluoroelastomeric composition is preferably cured attemperatures and for times sufficient to allow the curing reaction toproceed until the curable perfluoropolymers in the composition aresubstantially cured, preferably at least 70% cured. Preferred curingtemperatures and times are about 150° C. to about 250° C., for about 5to about 40 minutes. Following curing, an optional postcure may be used.Acceptable postcure temperatures and times are about 250° C. to about320° C. for about 5 to about 48 hours.

While curing, the curable perfluoroelastomeric compositions describedherein can be formed into a molded article while simultaneously curingusing heat and pressure applied by to a mold. Preferably, the combinedcurable perfluoropolymers are formed into a preform, such as an extrudedrope or other shape useful for including the preform in a mold having arecess shaped to receive the preform and for forming a molded articlewhile curing.

In addition to fillers, it is within the scope of the invention toinclude additional curable and noncurable perfluoropolymers havingvaried types, including the same or different cure site monomers tothose preferred herein. Additional curatives and cure accelerators,either to work with or accelerate the cure of the first perfluoropolymerand/or the second perfluoropolymer or to cure and/or accelerate cure ofany additional optional curable perfluoropolymers may also be includedherein. Noncurable perfluoropolymers include those which lack a reactivecure site and are formed from one or more ethylenically unsaturatedmonomers (such as TFE, HFP and PAVE). Additional curableperfluoropolymers may be any of the curable perfluoropolymers notedherein as well as those having cure sites suitable for crosslinking withorganic peroxide cure systems as are known in the art, tetraphenyl tincures, bisaminophenyl-based cures and the like. Such polymers may beadded to develop alternative blends and to modify the properties of thecompositions noted herein.

The perfluoroelastomers of the invention are alternatives to and in somegenerally show improved properties in comparison to semicrystallinefluoroplastic-filled FFKM compositions as used in the prior art. Thecompositions can be made without additional use of such fluoroplasticparticle fillers and without the need for high temperature mixing. Thehigher TFE content of the second polymer while allowing the curedperfluoropolymer in the composition to remain amorphous, changes thenature of the other perfluoropolymer such that the higher TFE contentperfluoropolymer acts in the role of a “filler” in the other curableperfluoropolymer. Thus, the molded articles produced by the elastomericcompositions of the present invention are more resilient to crackingunder harsh chemical, thermal and plasma conditions.

In contrast to the prior art, the compositions of the present inventionproduce an FFKM blend at a molecular level that results in desiredproperties for intended uses without the need for additional fillers.Further, in contrast to the prior art, the composition of the presentinvention, because it does not require a semicrystalline polymercomponent and remains in an amorphous state if unfilled, can be easilyprocessed.

As discussed, the amorphous, high-TFE curable perfluoropolymer in thecomposition is believed on theory to be instrumental to achievingdesired properties of the resultant perfluoroelastomeric composition.The mole percentage of TFE in the high TFE-content curableperfluoropolymer in the composition should not exceed about 95%, andparticularly should avoid approaching the crystalline point where amelting point would be discernible. The crosslinked elastomericcompositions and molded articles prepared therefrom display excellentthermal resistance with very low compression set. In addition, due totheir high purity and excellent plasma resistance, they can be used forsemiconductor sealing applications.

The hardness of preferred cross-linked perfluoroelastomer compositionsdescribed herein may be from about 40 to about 95 Shore A hardness, butis preferably at least about 50 Shore A, and more preferably at leastabout 55 Shore A, and most preferably at least about 60 Shore A. It isfurther preferred that hardness is no greater than about 95 Shore A,more preferred that it is no greater than about 90 Shore A and mostpreferred that it is no greater than about 85 Shore A. Such preferredhardness values provide more and increasingly superior sealingcharacteristics.

The resulting cured perfluoroelastomer compositions described hereinalso have superior chemical resistance, plasma resistance, goodmechanical strength and heat resistance. It is also possible to adjustthe hardness levels of the resulting perfluoroelastomer composition,with or without use of fillers, by using varying combinations of theperfluoropolymers noted herein. The outgassing component released fromthe resulting perfluoroelastomer compositions may also be reducedthereby assisting in avoidance of environmental pollution. It is also,therefore, useful for sealing semiconductor equipment, as an O-ring,square ring, corner ring, gasket, packing, oil seal, pairing seal, lipseal, door seal and the like. Such seals and related gasketing productscan be used in various types of semiconductor processing equipment forproviding semiconductor products having higher demands in manufactureand clarity, such as liquid crystal or plasma panel displays.

Exemplary equipment in which sealing products formed from theperfluoropolymer compositions herein may be used include etchingequipment, such as dry-etching, plasma-etching, reactive ion-etching,reactive ion beam-etching, sputter-etching, ion beam etching, wetetching and ashing equipment; cleaning apparatuses such as dry-etchingcleaning, UV/O₃ cleaning, ion beam cleaning, laser beam cleaning, plasmacleaning and gas etching cleaning apparatuses; extractor cleaningapparatuses, such as Soxhlet extraction cleaning, high-temperature,high-pressure extractor cleaning, microwave extractor cleaning, andsupercritical extractor cleaning apparatuses; exposure devices such assteppers and coater developers; polishing apparatuses such as CMPequipment; coating equipment such as CVD and sputtering equipment; anddiffusion-ion implantation equipment such as oxidation diffusionequipment and ion implantation equipment.

In one preferred best mode embodiment, the present invention relates toa fluorine-containing elastomer composition comprising two or more kindsof perfluoroelastomers, referred to herein as perfluoroelastomers (A),having different contents of a perfluoroalkylvinyl ether (PAVE) unit(a).

In the two or more kinds of perfluoroelastomers (A), there is adifference in the content of PAVE unit (a) between any two kinds ofperfluoroelastomers (A) that is preferably not less than 5% by mole,more preferably not less than 8% by mole, further preferably not lessthan 10% by mole, from the viewpoint of easy adjustment of hardness of acrosslinked article. In addition, the difference in a content of thePAVE unit (a) in each kind of perfluoroelastomer (A) is preferably notmore than 25% by mole, more preferably not more than 20% by mole,further preferably not more than 15% by mole, in that a glass transitiontemperature of the perfluoroelastomer having a smaller content of PAVEunit (a) is not elevated.

In addition, in this embodiment, in any two kinds of perfluoroelastomers (A) among two or more kinds of perfluoroelastomers (A),assuming that the perfluoroelastomer having the larger content of PAVEunit (a) is referred to as a perfluoroelastomer (A1) and theperfluoroelastomer having the smaller content of PAVE unit (a) isreferred to as a perfluoroelastomer (A2), the content of PAVE unit (a)in the perfluoroelastomer (A1) is preferably not less than 38% by mole,more preferably not less than 40% by mole, in that a crosslinking speedof the composition is faster. Also the content of PAVE in theperfluoroelastomer (A1) is preferably not more than 50% by mole, morepreferably not more than 45% by mole, further preferably not more than42% by mole, in that a polymerization rate in synthesizing a polymer ishigher.

In this embodiment, the content of PAVE in the perfluoroelastomer (A2)is preferably not less than 18% by mole, more preferably not less than21% by mole, further preferably not less than 25% by mole, from theviewpoint of a low glass transition temperature and satisfactory lowtemperature properties. Also the content of PAVE in theperfluoroelastomer (A2) is preferably not more than 35% by mole, morepreferably not more than 32% by mole, further preferably not more than30% by mole, from the viewpoint of increase in hardness of a crosslinkedarticle, thus enhancing sealing property of the sealing material.

Further, in this embodiment, a third perfluoroelastomer other than theperfluoroelastomers (A1) and (A2) may be mixed into the composition.

If only perfluoroelastomers having a smaller content of PAVE unit areused, a crosslinking time becomes longer. On the contrary, according tothe present invention, as mentioned above, shortening of a crosslinkingtime can be achieved by combining at least two kinds ofperfluoroelastomers, that is, one having a larger content of PAVE unitand another one having a smaller content of PAVE unit. Further hardnessof an obtained molded article can be easily adjusted by combining suchtwo kinds of perfluoro elastomers.

In this case, examples of PAVE are, as set forth in the above-notedembodiments, for instance, perfluoromethylvinyl ether (PMVE),perfluoropropylvinyl ether (PPVE) and the like. These can be used aloneor can be used in optional combination thereof to such an extent not toimpair the effect of the present invention.

Among these, PMVE is preferable from the viewpoint of an excellentmechanical strength of a cured article.

It is also preferable in this embodiment, that the perfluoroelastomer(A) further contains a monomer unit (b) having at least one kindselected from the group consisting of a nitrile group, a carboxyl groupand an alkoxycarbonyl group.

From the viewpoint of enhancing crosslinkability of the crosslinkableelastomer, the content of monomer unit (b) in perfluoroelastomer (A) isnot less than 0.1% by mole, preferably not less than 0.2% by mole, morepreferably not less than 0.3% by mole. In addition, the content ofmonomer unit (b) in the perfluoroelastomer (A) is not more than 2.0% bymole, preferably not more than 1.0% by mole, more preferably not morethan 0.5% by mole in that the amount of expensive monomer unit (b) canbe reduced.

Examples of the monomer unit (b) are, for instance, monomers representedby the formula (A) as noted hereinabove:

CF₂═CFO(CF₂CF(CF₃)O)_(m)(CF₂)_(n)—X¹  (A)

wherein m is 0 or an integer of 1 to 5, n is an integer of 1 to 3, X¹ isa nitrile group, a carboxyl group or an alkoxycarbonyl group. These canbe used alone or can be used in optional combination thereof.

The nitrile group, carboxyl group or alkoxycarbonyl group can functionas a cure site. In addition, from the viewpoint of excellentcrosslinkability, the monomer unit (b) is preferably a nitrilegroup-containing monomer in which a cure site is a nitrile group.

Examples of the monomer unit (b) are monomers represented by theformulae (1) to (17) in a manner as noted above:

CY₂═CY(CF₂)_(n)—X²  (1)

wherein Y is hydrogen atom or fluorine atom, n is an integer of 1 to 8,

CF₂═CFCF₂R_(f) ²—X²  (2)

where R_(f) ² is —(OCF₂)_(n)— or —(OCF₂)_(n)—, n is 0 or an integer of 1to 5,

CF₂═CFCF₂(OCF(CF₃)CF₂)_(m)(OCH₂CF₂CF₂)_(n)OCH₂CF₂—X²  (3)

wherein m is 0 or an integer of 1 to 5, n is 0 or an integer of 1 to 5,

CF₂═CFCF₂(OCH₂CF₂CF₂)_(m)(OCF(CF₃)CF₂)_(n)OCF(CF₃)—X²  (4)

wherein m is 0 or an integer of 1 to 5, n is 0 or an integer of 1 to 5,

CF₂═CF(OCF₂CF(CF₃))_(m)O(CF₂)_(n)—X²  (5)

wherein m is 0 or an integer of 1 to 5, n is an integer of 1 to 8,

CF₂═CF(OCF₂CF(CF₃))_(m)—X²  (6)

wherein m is an integer of 1 to 5,

CF₂═CFOCF₂(CF(CF₃)OCF₂)_(n)CF(—X²)CF₃  (7)

wherein n is an integer of 1 to 4,

CF₂═CFO(CF₂)_(n)OCF(CF₃)—X²  (8)

wherein n is an integer of 2 to 5,

CF₂═CFO(CF₂)_(n)—(C₆H₄)—X²  (9)

wherein n is an integer of 1 to 6,

CF₂═CF(OCF₂CF(CF₃))_(n)OCF₂CF(CF₃)—X²  (10)

wherein n is an integer of 1 to 2,

CH₂═CFCF₂O(CF(CF₃)CF₂O)_(n)CF(CF₃)—X²  (11)

wherein n is 0 or an integer of 1 to 5,

CF₂═CFO(CF₂CF(CF₃)O)_(m)(CF₂)_(n)—X²  (12)

wherein m is 0 or an integer of 1 to 5, n is an integer of 1 to 3,

CH₂═CFCF₂OCF(CF₃)OCF(CF₃)—X²  (13)

CH₂═CFCF₂OCH₂CF₂—X²  (14)

CF₂═CFO(CF₂CF(CF₃)O)_(m)CF₂CF(CF₃)—X²  (15)

wherein m is an integer of not less than O,

CF₂═CFOCF(CF₃)CF₂O(CF₂)_(n)—X²  (16)

wherein n is an integer of not less than 1,

CF₂═CFOCF₂OCF₂CF(CF₃)OCF₂—X²  (17)

in which in the formulae (1) to (17), X² is a nitrile group (—CN group),a carboxyl group (—COOH group) or an alkoxycarbonyl group (—COOR⁵,wherein R⁵ is an alkyl group having 1 to 10 carbon atoms which may havefluorine atom). Among these, perfluorinated compounds containing nohydrogen atom are preferable from the viewpoint of excellent heatresistance of the perfluoroelastomer (A) and for preventing decrease ofa molecular weight due to chain transfer when synthesizing theperfluoroelastomer by polymerization reaction. In addition, a compoundhaving a CF₂═CFO— structure is preferable from the viewpoint ofexcellent polymerization reactivity with tetrafluoroethylene.

Examples of such perfluoroelastomers (A) are those disclosed in JapaneseKokai No. 9-512569A, International Application WO 00/29479, and JapaneseKokai No. 11-92529A, etc.

Those perfluoroelastomers (A) in this embodiment can be prepared byknown methods.

The radical polymerization initiator used in this embodiment of thepresent invention may be one that is used for polymerization offluorine-containing rubbers, and examples thereof are organic andinorganic peroxides and azo compounds. Represented initiators arepersulfates, percarbonates, peresters and the like, and a preferableinitiator is APS. APS may be used alone or can be used in combinationwith reducing agents such as sulfites and sulfites.

As noted elsewhere herein, the emulsifier used for emulsionpolymerization can be selected from a wide range, and from the viewpointof inhibiting a chain transfer reaction to the emulsifier moleculeswhich occurs during the polymerization, salts of carboxylic acid havinga fluorocarbon chain or a fluoropolyether chain are preferable. Theamount of the emulsifier is preferably about 0.05 to 2% by weight,particularly preferably 0.2 to 1.5% by weight based on the added water.

The monomer mixture gas used in the present invention is explosive asdescribed in Advances in Chemistry Series, G. H. Kalb, et al., 129, 13(1973), and therefore it is necessary to take any measures forpolymerization equipment not to cause sparking which becomes an ignitionsource.

The polymerization pressure can be changed in a wide range, andgenerally is within a range from 0.5 to 7 MPa. The higher thepolymerization pressure is, the higher a polymerization rate is.Accordingly from the viewpoint of enhancement of productivity, thepolymerization pressure is preferably not less than 0.7 MPa.

For introducing at least one selected from the group consisting of anitrile group, a carboxyl group and an alkoxycarbonyl group to thefluorine-containing elastomer used in the present invention, asmentioned above, there is a method of copolymerizing by adding a monomerhaving a cure site when preparing the fluorine-containing elastomer inthis embodiment. An example of another method is a method of subjectinga polymerization product to acid treatment to convert a group such as ametallic salt or ammonium salt of a carboxylic acid contained in thepolymerization product to carboxyl group. An example of a suitable acidtreatment method is a method of washing with hydrochloric acid, sulfuricacid or nitric acid or a method of decreasing a pH value of a mixturesystem after the polymerization reaction to 3 or less by using thementioned acid.

In addition, it is possible to introduce a carboxyl group by oxidizing acrosslinkable elastomer containing iodine or bromine with a fumingnitric acid.

It is preferable that the fluorine-containing elastomer composition ofthis embodiment of the present invention comprises the crosslinkingagent (B) crosslinkable with the group of the above-mentionedfluorine-containing elastomer being capable of acting as a cure site.

The crosslinking agent(s) (B) used in the present invention is at leastone crosslinking agent selected from the group consisting of an oxazolecrosslinking agent, an imidazole crosslinking agent, a thiazolecrosslinking agent, a triazine crosslinking agent, an amidoximecrosslinking agent and an amidrazone crosslinking agent. Of these, animidazole crosslinking agent is preferable in that a crosslinked articlehaving excellent mechanical strength, heat resistance, chemicalresistance and cold resistance, particularly a crosslinked article beingexcellent in heat resistance and cold resistance in good balance can beprovided.

From the viewpoint of heat resistance, the preferred examples of anoxazole crosslinking agent, an imidazole crosslinking agent, a thiazolecrosslinking agent and a triazine crosslinking agent is at least onecompound selected from the group consisting of a compound containing atleast two crosslinkable reaction groups represented by the formula (II)as noted above:

wherein R¹ groups are the same or different and each is —NH₂, —NHR², —OHor —SH; R² is a monovalent organic group,a compound represented by the formula (III):

wherein R³ is —SO₂—, —O—, —CO—, an alkylene group having 1 to 6 carbonatoms, a perfluoroalkylene group having 1 to 10 carbon atoms or a singlebond; R⁴ is

a compound represented by the formula (IV):

in which R_(f) ¹ is a perfluoroalkylene group having 1 to 10 carbonatoms, and a compound represented by the formula (V):

in which n is an integer of 1 to 10.

Of these compounds, as with other embodiments noted herein, the compoundcontaining at least two crosslinkable reaction groups represented by theformula (II) is preferable in that heat resistance is enhanced due tostabilization by aromatic rings after the crosslinking.

The compound containing at least two crosslinkable reaction groupsrepresented by the formula (II) is preferably one having 2 or 3crosslinkable reaction groups, more preferably one having 2crosslinkable reaction groups. When the number of crosslinkable reactiongroups represented by the formula (II) is less than 2, crosslinkingcannot be achieved.

R² contained in the substituent R¹ of the crosslinkable reaction grouprepresented by the formula (II) is a monovalent organic group other thanhydrogen atom. Since an N—R² bond is higher in oxidation resistance thana N—H bond, it is preferable to use —NHR² as the substituent R¹ as notedabove.

The monovalent organic group is not limited particularly, and examplesthereof are an aliphatic hydrocarbon group, a phenyl group and a benzylgroup. Specifically, for example, at least one of R² is a lower alkylgroup having 1 to 10, particularly 1 to 6 carbon atoms such as —CH₃,—C₂H₅ or —C₃H₇; a fluorine atom-containing lower alkyl group having 1 to10, particularly 1 to 6 carbon groups such as —CF₃, —C₂F₅, —CH₂F,—CH₂CF₃ or —CH₂C₂F₅; a phenyl group; a benzyl group; a phenyl group or abenzyl group, in which 1 to 5 hydrogen atoms are substituted by fluorineatoms such as —C₆F₅ or —CH₂C₆F₅; or a phenyl group or a benzyl group, inwhich 1 to 5 hydrogen atoms are substituted by —CF₃ such as—C₆H_(5-n)(CF₃)_(n) or —CH₂C₆H_(5-n)(CF₃)_(n) wherein n is an integer of1 to 5.

Among these, a phenyl group and —CH₃ are preferable from the viewpointof especially excellent heat resistance, satisfactory crosslinkabilityand relatively easy synthesis.

From the viewpoint of easy synthesis, preferable as the crosslinkingagent (B) are compounds which have two crosslinkable reaction groupsrepresented by the formula (II) and are represented by the formula(VIII) as noted above:

wherein R¹ is as defined above, R⁶ is —SO₂—, —O—, —CO—, an alkylenegroup having 1 to 6 carbon atoms, a perfluoroalkylene group having 1 to10 carbon atoms, a single bond or a group represented by:

Preferable examples of alkylene groups having 1 to 6 carbon atoms, asnoted above, are methylene, ethylene, propylene, butylene, pentylene,hexylene and the like. Examples of perfluoroalkylene groups having 1 to10 carbon atoms are

and the like. These compounds are known as examples of bisdiaminophenylcompound in Japanese Patent No. 2-59177B, and Japanese Kokai No.8-120146A, etc.

Among these compounds, more preferable compounds as the crosslinkingagent (B) are compounds represented by the formula (X):

wherein R⁷ groups are the same or different and each is hydrogen atom,an alkyl group having 1 to 10 carbon atoms; an alkyl group having 1 to10 carbon atoms and containing fluorine atom; a phenyl group; a benzylgroup; or a phenyl group or benzyl group, in which 1 to 5 hydrogen atomsare replaced by fluorine atoms and/or —CF₃.

Non-limiting examples thereof are as with other embodiments herein, forinstance, 2,2-bis(3,4-diaminophenyl)hexafluoropropane,2,2-bis[3-amino-4-(N-methylamino)phenyl]hexafluoropropane,2,2-bis[3-amino-4-(N-ethylamino)phenyl]hexafluoropropane,2,2-bis[3-amino-4-(N-propylamino)phenyl]hexafluoropropane,2,2-bis[3-amino-4-(N-phenylamino)phenyl]hexafluoropropane,2,2-bis[3-amino-4-(N-perfluorophenylamino)phenyl]hexafluoropropane,2,2-bis[3-amino-4-(N-benzylamino)phenyl]hexafluoropropane, and the like.Of these, from the viewpoint of excellent heat resistance,2,2-bis[3-amino-4-(N-methylamino)phenyl]hexafluoropropane,2,2-bis[3-amino-4-(N-ethylamino)phenyl]hexafluoropropane,2,2-bis[3-amino-4-(N-propylamino)phenyl]hexafluoropropane and2,2-bis[3-amino-4-(N-phenylamino)phenyl]hexafluoropropane arepreferable, and from the viewpoint of particularly excellent heatresistance, 2,2-bis[3-amino-4-(N-phenylamino)phenyl]hexafluoropropane ispreferable.

The bisamidoxime crosslinking agent, bisamidrazone crosslinking agent,bisaminophenol crosslinking agent, bisaminothiophenol crosslinking agentor bisdiaminophenyl crosslinking agent react with a nitrile group, acarboxyl group or an alkoxycarbonyl group of the fluorine-containingelastomer and form an oxazole ring, a thiazole ring, an imidazole ringor a triazine ring to provide a crosslinked article.

An amount of the crosslinking agent (B) is preferably not less than 0.3part by weight, more preferably not less than 0.5 part by weight,further preferably not less than 0.7 part by weight based on 100 partsby weight of the elastomer, from the viewpoint of enhancingcrosslinkability of the composition. In addition, the amount of thecrosslinking agent (B) is preferably not more than 10.0 parts by weight,more preferably not more than 2.0 parts by weight based on 100 parts byweight of the elastomer.

In the present invention, in addition to the above-mentionedcrosslinking agents, other crosslinking agents can be used together.

When the fluorine-containing elastomer contains a nitrile group, thefluorine-containing elastomer composition in this embodiment of thepresent invention may comprise an organotin compound such astetraphenyltin, triphenyltin or the like because the nitrile group formsa triazine ring, thus making it possible to achieve triazinecrosslinking.

In this embodiment of the present invention, an amount of such anorganotin compound is preferably 0.05 to 10 parts by weight, morepreferably 1 to 5 parts by weight based on 100 parts by weight of thefluorine-containing elastomer. When the amount of organotin compound isless than 0.05 part by weight, there is a tendency that thefluorine-containing elastomer is not sufficiently crosslinked, and whenthe amount of organotin compound is more than 10 parts by weight,physical properties of a crosslinked article tends to be deteriorated.

In the fluorine-containing elastomer composition of this embodiment ofthe present invention, usual additives may be added, as the casedemands, to crosslinkable elastomer compositions, for example, a filler,a processing aid, a plasticizer and a colorant may be blended thereto.In addition, one or more usual crosslinking agents or crosslinkingaccelerators different from the above-mentioned ones may be blended tothe composition. Also, a different kind of elastomer may be mixed to anextent not to impair the effects of the present invention.

Examples of a filler for this embodiment are organic fillers, and fromthe viewpoint of heat resistance and plasma resistance (reduced numberof particles and low weight reduction rate at emission of plasma), thereare preferably exemplified organic pigments; imide fillers having animide structure such as polyimide, polyamide imide and polyetherimide;ketone engineering plastics such as polyether ether ketone (PEEK) andpolyether ketone (PEK), and organic pigments are particularlypreferable.

Examples of organic pigments for use in this embodiment are condensedazo pigments, isoindolenone pigments, quinacridone pigments,diketopyrrolopyrrole pigments, anthraquinone pigments, and the like.Among these pigments, from the viewpoint of excellent heat resistanceand chemical resistance and less effect on characteristics of a moldedarticle, quinacridone pigments, diketopyrrolopyrrole pigments andanthraquinone pigments are preferable, and quinacridone pigments aremore preferable.

Further the fluorine-containing crosslinkable composition of thisembodiment of the present invention may contain a general filler.

Examples of such general fillers are organic fillers made of engineeringplastics such as polyarylate, polysulfone, polyether sulfone,polyphenylene sulfide, polyoxybenzoate and polytetrafluoroethylenepowder; metallic oxide fillers such as aluminum oxide, silicon oxide,yttrium oxide and titanium oxide; metallic carbides such as siliconcarbide and aluminum carbide, metallic nitride fillers such as siliconnitride and aluminum nitride; and inorganic fillers such as aluminumfluoride, carbon fluoride, barium sulfate, carbon black, silica, clayand talc.

Among these fillers, from the viewpoint of an effect of shieldingvarious plasmas, aluminum oxide, yttrium oxide, silicon oxide, polyimideand carbon fluoride are preferable.

Also, the above-mentioned inorganic fillers and organic fillers may beused alone or may be blended in combination of two or more thereof.

The fluorine-containing elastomer composition of this embodiment of thepresent invention can be prepared by mixing each of the above-mentionedcomponents by using usual processing equipment for rubber, for example,an open roll, Banbury mixer, kneader, or the like. In addition, thecomposition can be prepared also by a method of using a closed mixer anda method of co-coagulation through emulsion mixing.

A hardness in Shore A of a crosslinked article obtained by crosslinkingthe fluorine-containing elastomer of this embodiment of the presentinvention is preferably not less than 50, more preferably not less than55, further preferably not less than 60 in that sealing property of thesealing material made of the elastomer composition of the presentinvention is satisfactory. In addition, the hardness of a crosslinkedarticle is preferably not more than 95, more preferably not more than90, further preferably not more than 85 in that sealing property of thesealing material made of the elastomer composition of the presentinvention is satisfactory.

A crosslinked article obtained by crosslinking and molding thefluorine-containing elastomer composition of this embodiment of thepresent invention is excellent in chemical resistance, mechanicalstrength and heat resistance. Also, according to this embodiment of thepresent invention, since adjustment of the hardness can be carried outby combining two kinds of perfluoroelastomers, the hardness can beadjusted to a desired one even without adding a filler. In this case,the cured article is suitable as a sealing material for sealing of, forexample, semiconductor equipment from the viewpoint of improvement inreduction of pollution of working environment because outgas componentgenerated from the cured article is reduced. Examples of the sealingmaterial are O-ring, square ring, gasket, packing, oil seal, bearingseal, lip seal, etc.

In the present invention, the semiconductor manufacturing equipment isnot limited particularly to equipment for producing semiconductors andencompasses whole manufacturing equipment used in the field ofsemiconductors where a high degree of cleanliness is required, such asequipment for manufacturing a liquid crystal panel and a plasma panel.Examples of the semiconductor manufacturing equipment are as follows.

(1) Etching System

-   -   Dry etching equipment    -   Plasma etching machine    -   Reactive ion etching machine    -   Reactive ion beam etching machine    -   Sputter etching machine    -   Ion beam etching machine    -   Wet etching equipment    -   Ashing equipment

(2) Cleaning System

-   -   Dry etching cleaning equipment    -   UV/03 cleaning machine    -   Ion beam cleaning machine    -   Laser beam cleaning machine    -   Plasma cleaning machine    -   Gas etching cleaning machine    -   Extractive cleaning equipment    -   Soxhlet extractive cleaning machine    -   High temperature high pressure extractive cleaning machine    -   Microwave extractive cleaning machine    -   Supercritical extractive cleaning machine

(3) Exposing System

-   -   Stepper    -   Coater and developer

(4) Polishing System

-   -   CMP equipment

(5) Film Forming System

-   -   CVD equipment    -   Sputtering equipment

(6) Diffusion and Ion Implantation System

-   -   Oxidation and diffusion equipment    -   Ion implantation equipment

The invention will now be explained with Examples but is not limited tothe Examples.

EXAMPLE 1

A compound used in this Example is shown below. The compound (NPh-AF)represented below is used as a curing or crosslinking agent.

Preparation Example 1 Synthesis of Perfluoroelastomer (1)

Into a 6-liter stainless steel autoclave having no ignition source werepoured 2.34 liters of pure water, 23.4 g of

as an emulsifying agent and 0.21 g of (NH₄)₂CO₃, and the inside of thesystem was sufficiently replaced with nitrogen gas and subjected todeaeration. Then, the autoclave was heated up to 52° C. with stirring at600 rpm, and a gas mixture of tetrafluoroethylene (TFE) andperfluoro(methyl vinyl ether) (PMVE) (molar ratio of TFE/PMVE=22/78) wasintroduced so that the inside pressure became 0.78 Mpa·G. Then, afterintroducing 0.82 g of CF₂═CFO(CF₂)₅CN with pressurized nitrogen gas, asolution prepared by dissolving 12.3 g of ammonium persulfate (APS) in30 g of water, was introduced with pressurized nitrogen gas to initiatea reaction.

As the polymerization proceeded, the inside pressure of the reactordecreased, and pressurized TFE and PMVE were introduced so that theinside pressure became 0.78 MPa·G. Until completion of thepolymerization, 323 g of TFE and 356 g of PMVE were introduced in aspecific ratio. During the reaction, pressurized CF₂═CFO(CF₂)₅CN wasintroduced 17 times, totaling 14.67 g to obtain 2,989 g of an aqueousdispersion having a solids content of 21.2% by weight.

Out of the obtained aqueous dispersion, 500 g was distilled with 500 gwater, and the distilled solution was slowly added to 2,800 g of 3.5% byweight aqueous solution of hydrochloric acid with stirring. Aftercompletion of the addition, the solution was stirred for five minutes,and then a coagulated product was filtered off. The obtained polymer waspoured into 2 kg of HCFC-141b, followed by 5-minute stirring andfiltering off again. Thereafter washing with HCFC-141 b and filteringoff were repeated four more times, followed by vacuum drying at 60° C.for 72 hours to obtain 110 g of a polymer (Perfluoroelastomer (1)).

According to F-NMR analysis, contents of each monomer of the obtainedPerfluoroelastomer (1) are as shown in Table 1.

EXAMPLE 2 Preparation Example 2 Synthesis of Perfluoroelastomer (2)

Into a 6-liter stainless steel autoclave having no ignition source werepoured 2.34 liters of pure water, 23.4 g of

as an emulsifying agent and 0.21 g of (NH₄)₂CO₃, and the inside of thesystem was sufficiently replaced with nitrogen gas and subjected todeaeration. Then the autoclave was heated up to 52° C. with stirring at600 rpm, and a gas mixture of TFE and PMVE (molar ratio ofTFE/PMVE=41/59) was introduced so that the inside pressure became 0.78Mpa·G. Then, after introducing 0.87 g of CF₂═CFO(CF₂)₅CN withpressurized nitrogen gas, a solution prepared by dissolving 12.3 g ofAPS in 30 g of water, was introduced with pressurized nitrogen gas toinitiate a reaction.

As the polymerization proceeded, the inside pressure of the reactordecreased, and pressurized TFE and PMVE were introduced so that theinside pressure became 0.78 MPa·G. Until completion of thepolymerization, 400 g of TFE and 284 g of PMVE were introduced in aspecific ratio. During the reaction, pressurized CF₂═CFO(CF₂)₅CN wasintroduced 17 times totaling 14.72 g to obtain 3,087 g of an aqueousdispersion having a solids content of 22.5% by weight.

Out of the obtained aqueous dispersion, 500 g was distilled with 500 gwater, and the distilled solution was slowly added to 2,800 g of 3.5% byweight aqueous solution of hydrochloric acid with stirring. Aftercompletion of the addition, the solution was stirred for five minutes,and then a coagulated product was filtered off. The obtained polymer waspoured into 2 kg of HCFC-141 b, followed by 5 minutes of stirring andfiltering off again. Thereafter washing with HCFC-141b and filtering offwere repeated four more times, followed by vacuum drying at 60° C. for72 hours to obtain 110 g of a polymer (Perfluoroelastomer 2).

According to F-NMR analysis, contents of each monomer of the obtainedPerfluoroelastomer (2)

TABLE 1 Content (% by mole) Perfluoroelastomer (1) Perfluoroelastomer(2) PMVE 41.7 30.2 TFE 57.9 69.4 CF₂═CFO(CF₂)₅CN 0.43 0.43

EXAMPLE 3

Perfluoroelastomer (1) from Example 1, Perfluoroelastomer (2) fromExample 2 and NPh-AF (shown above) as a cross-linking agent were mixedin amounts as shown in Table 2, and kneaded with an open roll to preparea crosslinkable fluorine-containing elastomer composition.

This fluorine-containing elastomer composition was subjected tocrosslinking by pressing at 180° C. for 20 minutes and furthercrosslinking in an oven at 290° C. for 18 hours to make a test sampleO-ring (P-24). With respect to this test sample, crosslinkability atcrosslinking and physical properties in the normal state were measuredby the following methods. The results are shown in Table 2.

Crosslinkability: With respect to each crosslinkable composition, avulcanization curve was obtained at 180° C. by using JSR typeCurastometer Model II, and a minimum torque (M_(L)), a maximum torque(M_(H)), and induction time (T₁₀) and an optimum vulcanization time(T₉₀) were determined.

Physical Properties in the Normal State: According to JIS K 6301, a 100%modulus (M₁₀₀), a tensile strength (T_(B)), an elongation (E_(B)) andhardness (H_(s)) of a 2 mm thick crosslinked article in a normal state(25° C.) were measured.

COMPARATIVE EXAMPLE 1

A composition was prepared in the same manner as in Example 3 with theexception that only Perfluoroelastomer (1) was used as aperfluoroelastomer instead of a combination use of Perfluoroelastomers(1) and (2). Then crosslinkability at crosslinking and physicalproperties in a normal state were measured in the same manner as Example3. The results are shown also in Table 2.

COMPARATIVE EXAMPLE 2

A composition was prepared in the same manner as in Example 3 with theexception that only Perfluoroelastomer (2) was used as aperfluoroelastomer instead of a combination use of Perfluoroelastomers(1) and (2). Then crosslinkability at crosslinking and physicalproperties in a normal state were measured in the same manner as Example3. The results are shown also in Table 2.

TABLE 2 Comparative Comparative Amount (parts per 100) Example 3 Example1 Example 2 Perfluoroelastomer (1) 50 100 — Perfluoroelastomer (2) 50 —100 NPh-AF 1.0 1.0 1.0 Results of evaluation Crosslinkability M_(L)(kgf) 0.72 0.42 1.12 M_(H) (kgf) 3.03 2.50 3.33 T₁₀ (min) 5.6 4.3 7.3T₉₀ (min) 16.3 9.5 44.5 Physical Properties in Normal State M₁₀₀ (MPa)2.1 1.3 3.2 T_(B) (MPa) 16.0 6.7 20.8 E_(B) (%) 250 275 225 H_(s) (ShoreA) 68 59 78

EXAMPLES 4-14

The elastomeric compositions in the Examples 4-14 were produced bymixing or blending the perfluoropolymers with any desired additives. Thepolymer(s) and any additives may be blended using an internal mixer suchas those commercially available from C. W. Brabender Instruments, Inc.of S. Hackensack, N.J. or other internal mixers such as are commerciallyavailable from Morijama of Farmingdale, N.Y. Examples 4-12 were preparedby blending in a two-roll mixer (also called “open mill mixer”), with6-inch diameter, using a regular rubber compounding mixing method knownin the art. The roll temperature was about 50° C. with a roll speed ofabout 25 to 35 rpm for a batch weight of 500 grams.

The method of preparation included adding the first polymer onto themill at 50° C. and mixing for approximately 8-9 minutes. After the firstcurable perfluoropolymer was sheeted out on the mill, the second curableperfluoropolymer was added. After mixing both polymers for another 3-4minutes, the curative was added and mixed thoroughly. After adding thecurative, the blend was cut and mixed on the rolls 3 times, and thencut/mixed 30 times. The blend was taken off the mill and cooled down toabout room temperature. Once cooled, the blend was placed back into themill and cut/mixed multiple times.

A standard regular rubber compounding procedure was used except for themixing temperature 50° C. and the cutting and remixing steps (3+30+30cut/remixing).

For Examples 13 and 14, the internal mixer first used was at 50° C. tomix a master batch concentrate by adding the first perfluoropolymer andthe curative based on the formulation of the master batch concentrate.The master batch included Polymer A in 100 parts by weight and NPh-AF(in an amount of 6.8 parts per hundred parts by weight). The masterbatch was then diluted to prepare the formulations noted for Examples 13and 14. The master batch concentrate was unloaded from the internalmixer and moved to an open mill. The same procedures as described abovewere followed for Examples 4-12 except for adding the master batchconcentrate having curatives in the last step (instead of the curativeonly).

It will be recognized that these procedures were for these examples onlyand that any other standard rubber compounding mixer or regular internalmixer could be used within the invention.

Examples of elastomer compositions and molded articles preparedaccording to the methods of the present invention are set forth below inTable 3. Included in Table 3 are the physical characteristics ofelastomers formed by the present invention. Examples 4-14 were testedfor properties using ASTM procedures identified in Table 4, and thephysical property parameters were recorded: Tb (tensile at break in psi(MPa)); E_(B) (elongation at break in %); M₁₀₀ (100% modulus in psi(MPa)), Hardness (Durometer M) and Compression set of the O-ringsprepared from the elastomers.

The example compounds were prepared from a commercially availableperfluoropolymer composition and mixed as discussed herein. In theexamples, Polymer A from Daikin Industries is the first perfluoropolymeras defined herein and is a perfluoropolymer of TFE andperfluoromethylvinyl ether (PMVE) in a molar ratio of 60/40. Polymer Bfrom Daikin Industries is the second polymer used and is aperfluoropolymer of TFE and PMVE in a molar ratio of 70/30. In both ofPolymers A and B, there is 0.6 mole percent of a cure site monomerincluded a cyano-functional group for curing. The curative, NPh-AF is4,4′-[2,2,2-Trifluoro-1-(trifluoromethyl)ethylidene]bis[N1-phenyl-1,2-benzenediamine].Each of the components, Polymer A and B, and NPh-AF are commerciallyavailable. The weight percentage ratios of the resultant exampleelastomers (Examples 4-14) vary as described in Table 3. The compoundswere cured at 182° C. for 30 minutes followed by postcuring at 290° C.for 18 hours.

The molded articles, most commonly an O-ring, seal or gasket, formedfrom an elastomer of the present invention, are described herein. Sealscan be formed from the perfluoropolymers by a variety of processingmethods, such as compression molding, injection molding, extrusion, etc.Molding was used in the Examples herein.

As illustrated in Table 3, after testing in remote NF₃ plasma at hightemperature, the samples showed insignificant weight loss. The sampleintegrity and surface appearance showed no significant change. Comparedto the commercial samples as controls, the working examples displaybetter resistance to remote NF₃ plasma. In direct plasma environments(O₂, O₂+CF₄), the results are comparable to the commercial products.

O-rings were formed from the resultant elastomers of Examples 4-14 forevaluation of compression set. Examples 4-14 each showed less than 25percent compression set after 300° C. for 70 hours under 25% deflectionand showed less than 40 percent compression set after 300° C. for 168hours under 25% deflection. This is a significant improvement in theart.

The O-rings formed from the elastomers of Examples 4-14 were subjectedto a plasma gas environment and evaluated. The percent loss is definedfor each in Table 3 based on the internal screening method listed inTable 4.

TABLE 3 Formulation Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11Ex. 12 Ex. 13 Ex. 14 Polymer B (weight ratio) 50 50 50 65 65 65 35 35 3550 50 Polymer A (weight ratio) 50 50 50 35 35 35 65 65 65 50 50 NPh-AF0.7 0.8 0.9 0.7 0.8 0.9 0.7 0.8 0.9 0.9 0.9 T_(B): psi (MPa) 944 1049978 1388 1130 1370 847 933 894 1103 1052 (6.51) (7.23) (6.74) (9.57)(7.79) (9.45) (5.84) (6.43) (6.16) (7.61) (7.26) Eb (%) 271 262 261 263258 260 270 262 249 256 261 M₁₀₀: psi (MPa) 193 216 200 242 236 250 184198 217 231 217 (1.33) (1.49) (1.38) (1.67) (1.63) (1.72) (1.27) (1.37)(1.50) (1.59) (1.50) Density 2.055 2.0575 2.056 2.061 2.061 2.063 2.0502.056 2.055 2.054 2.057 Shore M Hardness 71 71.5 71.5 72.5 72.5 73 70 7070 71.5 Shore A Hardness 63.5 64 64.5 65 65.5 66.5 61.5 62 62.5 65.563.5 Compression set (%) 21.2 19.7 17.3 20.3 20.3 17.4 17.7 18.5 17.117.1 17.7 (300° C./70 hrs) Compression set (%) 33.5 30.9 29.4 27.6 33.530.0 35.0 25.2 31.4 31.6 29.7 (300° C./168 hrs) Stiction: lbs (N) 41.040.6 41.5 45.9 46.0 46.9 38.9 40.2 40.5 40.1 40.4 (182.4) (180.6)(184.6) (204.2) (204.6) (208.6) (173.0) (178.8) (180.1) (178.4) (179.7)NF₃ remote, 6 hrs/220° C. 0.023 0.022 −0.024 0.108 0.116 0.069 0.070−0.022 0.046 0.000 −0.023 (% loss) O₂ direct ICP, 30 min. 2.82 2.94 2.872.72 2.84 2.95 2.97 3.07 2.84 2.8 2.77 (% loss) O₂ + CF₄ direct ICP 2.982.89 2.93 2.92 2.98 2.91 2.95 3.29 2.91 2.95 3.02 (% loss) NF₃ remote,12 hrs/250° C. 0.084 0.006 −0.041 −0.001 0.065 0.034 0.039 0.073 0.0230.035 0.023 loss O₂ Direct, 80° C./60 min 4.243 4.395 4.690 4.718 5.0815.134 5.482 5.546 5.522 5.493 5.255 ICP (% loss) O₂ + CF₄ Direct/80°C./60 4.469 4.687 4.875 4.907 5.275 5.526 5.818 6.083 5.785 5.569 5.550min, ICP (% loss) RIE O₂ plasma, 90 min. 3.453 3.288 3.006 3.076 2.6093.234 3.235 3.331 3.413 3.377 3.586 (% loss)

TABLE 4 Properties Testing Method M_(H:) lb inch (N · m or ASTM D 5289,average of 2 min sets; 360° F. kg · f as noted) M_(L:) lb inch (N · m or(182.2° C.)/60 min. kg · f as noted) T₁₀ (min) T₅₀ (min) T₉₀ (min)T_(s2) (min) T_(b:) psi (MPa) Average of 10 O-rings, 20″/min, ASTM DE_(b) (%) 1414, ASTM D 412 M₁₀₀: psi (MPa) Density ASTM D 792 Shore MHardness ASTM D 2240 Shore A Hardness ASTM D 2240 Compression set (%)ASTM D 1414/ASTM D 395 average of 10 (300° C./70 h) Compression set (%)ASTM D1414/ASTM D395 average of 10 (300° C./168 h) Stiction: lbs. (N)Compression 25% between two Aluminum substrates, conditioning 392° F.(200° C.) for 24 hrs and cool for 1 h and then push O-ring of Al at0.5″/min (0.2 mm/second). NF₃ remote, NF₃/Ar 1:1, 3 Torr, 220° C. (setup 300° C.) 6 h/220° C. (% loss) NF₃ remote, NF₃/Ar 1:1, 3 Torr, 220° C.(set up 300° C.) 12 h/220° C. (% loss) O₂ direct ICP, Power 400 W, flow16 standard cm³ per 30 min. (% loss) minute, pressure: 10 Pa, time: 30min. O₂ + CF₄ Power 400 W, O₂/CF₄ 16/16standard cm³ per direct ICP (%loss) NF₃ remote, Power 2500 W, pressure 990 mTorr, NF₃ 400 12 h/250° C.(% loss)

O₂ Direct, Power 590 W, pressure 100 mTorr, O₂: 32 80° C./60 min ICP (%loss) O₂ + CF₄ Power 590 W, pressure 100 mTorr, O₂/CF₄ Direct/80° RIE O₂plasma Power 300 W, pressure 300 mTorr. O₂: 60 AEC, 4400 seconds (%loss) RIE O₂ + CF₄ Power 300 W, pressure 300 mTorr, O₂/CF₄: plasma, AEC,4400 30/30 standard cm³ per minute seconds (% loss)

indicates data missing or illegible when filed

EXAMPLE 15

As noted elsewhere herein, the various fluorine-containing elastomersand perfluoroelastomer blends described herein can be bonded and moldedonto metals and other substrates to form bonded products. Bondingsamples were prepared and evaluated using the current ASTM-D-429 methodA involving pulling two metal plates apart at a rate of 0.4 mm/second (1inch/minute) at room temperature and recording bonding force. A blend oftwo perfluoropolymers according to the invention was molded in betweentwo circular metal plate surfaces, each of which surface was treatedwith a bonding agent prior to the bonding process. The metal plates,which were 2 in (12.9 cm²) in surface area, were sandblasted with36-sized grit before use.

Perfluoroelastomer compound C was dissolved in Fluorinert® FC-77 to bondthe blended composition of Example 9 in Table 3 onto aluminum and steelsurfaces. Example 9's compositions included Polymer A in 35 parts perhundred, Polymer B in 65 parts per hundred and NPh-AF (in 0.9 parts perhundred). The bonding agent (Perfluoroelastomer compound C) included aperfluoroelastomer polymer having a nitrile-functionalized cure sitemonomer (FFKM, 100 parts), Aerosil® R972 (12 parts per hundred partsFFKM), 2,2-bis[3-amino-4-hydroxyphenyl]hexafluoropropane (1.5 parts perhundred curative), Cromophthal Blue A3R (0.5 parts per hundred as acolorant), Cromophthal Yellow 2RF (0.5 parts per hundred as a colorant),and Varox® DBPH-50 (1 part per hundred). In the polymer FFKM D, themolar ratio of TFE:PMVE: CSM of 53:44:3.

After dissolving Compound C in FC-77, the mixture was applied as a thinlayer to a metal substrate. The solution was allowed to dry for 30minutes and a pressed portion of the composition of Example 9 was moldedonto the substrates at 360° F. (182.2° C.) for 30 minutes, and thenpostcured at 550° F. (287.8° C.) for 22 hours.

Table 5 shows the results from the bonding force tests.

TABLE 5 Before After Bonding Force Bonding Agent Substrate PostcurePostcure lbs (N) Compound C in Al 2-bonded* 2-bonded 1337 (5947), FC-77,1:15  895 (3981) Compound C Al 2-bonded 2-bonded 1390 (6183), inFC-77,1:6 1449 (6445) Compound C in Steel 2-bonded 2-bonded 1436 (6387),FC-77, 1:15 1603 (7130) Compound C Steel bonded* bonded 1328 (5907), --in FC-77, 1:6 *“2-bonded” means that both samples made were bonded and“bonded” means that only one sample was made and tested.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

1. A fluorine-containing elastomer composition comprising a firstcurable perfluoropolymer comprising tetrafluoroethylene, a firstperfluoroalkylvinyl ether and at least one first cure site monomerhaving at least one functional group selected from the group consistingof nitrile, carboxyl and alkoxycarbonyl; and a second curableperfluoropolymer comprising tetrafluoroethylene, a secondperfluoroalkylvinyl ether and at least one second cure site monomerhaving at least one functional group selected from the group consistingof nitrile, carboxyl and alkoxycarbonyl, wherein the content of thefirst perfluoroalkylvinyl ether in the first curable perfluoropolymerand the content of the second perfluoroalkylvinyl ether in the secondcurable perfluoropolymer are different.
 2. A fluorine-containingelastomer composition comprising perfluoroelastomers (A) having atetrafluoroethylene unit, a perfluoroalkylvinyl ether unit (a) and amonomer unit (b) having at least one kind selected from the groupconsisting of a nitrile group, a carboxyl group and an alkoxycarbonylgroup, wherein the composition comprises two or more kinds ofperfluoroelastomers (A) having different contents of theperfluoroalkylvinyl ether unit (a).
 3. The fluorine-containing elastomercomposition of claim 2, wherein in two or more kinds ofperfluoroelastomers (A), a difference in the content ofperfluoroalkylvinyl ether unit (a) between any two kinds ofperfluoroelastomers (A) is 5 to 25% by mole.
 4. The fluorine-containingelastomer composition of claim 2, wherein the monomer unit (b) is anitrile group-containing monomer unit.
 5. The fluorine-containingelastomer composition of claim 1, wherein the perfluoroalkylvinyl etherunit (a) is a perfluoromethylvinyl ether unit.
 6. Thefluorine-containing elastomer composition of claim 1, further comprisinga crosslinking agent (B) being crosslinkable with at least one kindselected from the group consisting of a nitrile group, a carboxyl groupand an alkoxycarbonyl group of the monomer unit (b).
 7. Thefluorine-containing elastomer composition of claim 6, wherein an amountof the crosslinking agent (B) is 0.3 to 10.0 parts by mass based on 100parts by mass of the whole perfluoro elastomers.
 8. Thefluorine-containing elastomer composition of claim 5, wherein thecrosslinking agent (B) is a compound containing at least twocrosslinkable reaction groups represented by the formula (II):

wherein R³ groups are the same or different and each is —NH₂, —NHR², —OHor —SH; R² is a monovalent organic group, a compound represented by theformula (III):

wherein R³ is —SO₂—, —O—, —CO—, an alkylene group having 1 to 6 carbonatoms, a perfluoroalkylene group having 1 to 10 carbon atoms or a singlebond; R⁴ is

a compound represented by the formula (IV):

wherein R_(f) ¹ is a perfluoroalkylene group having 1 to 10 carbonatoms, and a compound represented by the formula (V):

wherein n is an integer of 1 to
 10. 9. A sealing material forsemiconductor manufacturing equipment made of the fluorine-containingelastomer composition of claim
 1. 10. A curable perfluoroelastomericcomposition comprising: a first curable perfluoropolymer comprisingtetrafluoroethylene, a first perfluoroalkylvinyl ether and at least onefirst cure site monomer having a cure site, wherein a molar ratio of thetetrafluoroethylene to the perfluoroalkylvinyl ether is about 0:100 toabout 65:35 molar percentage in the perfluoropolymer; a second curableperfluoropolymer comprising tetrafluoroethylene, a secondperfluoroalkylvinyl ether which may be the same or different from thefirst perfluoroalkylvinyl ether, and at least one second cure sitemonomer having a cure site which may be the same or different from theat least one first cure site monomer, wherein a molar ratio of thetetrafluoroethylene to the second perfluoroalkylvinyl ether is about65:35 to about 95:5 in the polymer; and at least one curative capable ofcuring the at least one first cure site monomer and the at least onesecond cure site monomer.
 11. The composition according to claim 10,wherein the first curable perfluoropolymer comprises about 0 to about58.5 mole percent of the tetrafluoroethylene, about 31.5 percent toabout 99.99 mole percent of the first perfluoroalkylvinyl ether andabout 0.1 mole percent to about 10 mole percent of the at least onefirst cure site monomer and the second curable perfluoropolymercomprises about 65 to about 85.5 mole percent of thetetrafluoroethylene, about 4.5 to about 35 mole percent of the secondperfluoroalkylvinyl ether and about 0.1 mole percent to about 10 molepercent of the at least one second cure site monomer.
 12. Thecomposition according to claim 11, wherein the first curableperfluoropolymer comprises about 49.8 to about 63.1 mole percent of thetetrafluoroethylene, about 49.75 to about 34 mole percent of the firstperfluoroalkylvinyl ether and about 0.5 mole percent to about 3 molepercent of the at least one first cure site monomer and the secondcurable perfluoropolymer comprises about 64.7 to about 82.5 mole percentof the tetrafluoroethylene, about 14.6 to about 34.83 mole percent ofthe second perfluoroalkylvinyl ether and about 0.5 mole percent to about3 mole percent of the at least one second cure site monomer.
 13. Thecomposition according to claim 10, wherein the first curableperfluoropolymer has a molar ratio in the first curable perfluoropolymerof the tetrafluoroethylene to the first perfluoroalkylvinyl ether ofabout 50:50 to about 65:35 and the second curable perfluoropolymer has amolar ratio in the second curable perfluoropolymer of thetetrafluoroethylene to the second perfluoroalkylvinyl ether of about65:35 to about 85:15.
 14. The composition according to claim 10, whereinthe composition comprises from about 0.6 to about 0.9 weight percentageof the curative.
 15. The composition according to claim 10, wherein thecure site of the at least one first cure site monomer and the cure siteof the at least one second cure site monomer each is a functional groupselected from the group consisting of a nitrile group, a carboxyl groupand an alkoxycarbonyl group.
 16. The composition according to claim 15,wherein the at least on first cure site monomer provides the functionalgroup on at least one terminal end of the first curable perfluoropolymerand/or depending from a polymer backbone of the first curableperfluoropolymer.
 17. The composition according to claim 15, wherein theat least one second cure site monomer provides the functional group onat least one terminal end of the first curable perfluoropolymer and/ordepending from a polymer backbone of the first curable perfluoropolymer.18. The composition according to claim 15, wherein the at least onecurative reacts with the functional group of the at least one first curesite monomer and/or the at least one second cure site monomer to formbenzoimidazole cross-linking structures.
 19. The composition accordingto claim 10, wherein the difference in molar percentage content betweenthe first perfluoroalkylvinyl ether and the second perfluoroalkylvinylether is about 5% to about 25%.
 20. The composition according to claim10, further comprising at least one additional curable perfluoropolymercomprising tetrafluoroethylene, a perfluoroalkylvinyl ether and a curesite monomer.
 21. A cured perfluoroelastomeric composition, comprising:a first perfluoroelastomer formed from a first curable perfluoropolymercomprising tetrafluoroethylene, a first perfluoroalkylvinyl ether and atleast one first cure site monomer having a cure site, wherein a molarratio of the tetrafluoroethylene to the perfluoroalkylvinyl ether isabout 0:100 to about 65:35 molar percentage in the perfluoropolymer; anda second perfluoroelastomer formed from a second curableperfluoropolymer comprising tetrafluoroethylene, a secondperfluoroalkylvinyl ether which may be the same or different from thefirst perfluoroalkylvinyl ether, and at least one second cure sitemonomer having a cure site which may be the same or different from theat least one first cure site monomer, wherein a molar ratio of thetetrafluoroethylene to the second perfluoroalkylvinyl ether is about65:35 to about 95:5 in the second curable perfluoropolymer.
 22. Thecomposition according to claim 21, wherein the first curableperfluoropolymer comprises about 0 to about 58.5 mole percent of thetetrafluoroethylene, about 31.5 percent to about 99.99 mole percent ofthe first perfluoroalkylvinyl ether and about 0.1 mole percent to about10 mole percent of the at least one first cure site monomer and thesecond curable perfluoropolymer comprises about 65.0 to about 85.5 molepercent of the tetrafluoroethylene, about 4.5 to about 35 mole percentof the second perfluoroalkylvinyl ether and about 0.1 mole percent toabout 10 mole percent of the at least one second cure site monomer. 23.The cured perfluoroelastomeric composition according to claim 21,wherein the first curable perfluoropolymer has a molar percentage ratioin the first curable perfluoropolymer of the tetrafluoroethylene to thefirst perfluoroalkylvinyl ether of about 50:50 to about 65:35 and thesecond curable perfluoropolymer has a molar percentage ratio in thesecond curable perfluoropolymer of the tetrafluoroethylene to the secondperfluoroalkylvinyl ether of about 65:35 to about 85:15.
 24. The curedperfluoroelastomeric composition according to claim 21, wherein the curesite of the at least one first cure site monomer and the cure site ofthe at least one second cure site monomer each is a functional groupselected from the group consisting of a nitrile group, a carboxyl groupand an alkoxycarbonyl group.
 25. The cured perfluoroelastomericcomposition according to claim 21, wherein at least one of the firstperfluoroelastomer and the second perfluoroelastomer has abenzoimidazole cross-linking structure.
 26. The curedperfluoroelastomeric composition according to claim 21, wherein a weightpercentage ratio of the first perfluoroelastomer to the secondperfluoroelastomer in the composition is about 1:99 to about 99:1. 27.The cured perfluoroelastomeric composition according to claim 26,wherein the weight percentage ratio of the first perfluoroelastomer tothe second perfluoroelastomer in the composition is about 20:80 to about80:20.
 28. The cured perfluoroelastomeric composition according to claim27, wherein the weight percentage ratio of the first perfluoroelastomerto the second perfluoroelastomer in the composition is about 75:25 toabout 55:45.
 29. The cured perfluoroelastomeric composition according toclaim 21, wherein the difference in molar percentage ratio of the firstperfluoroalkylvinyl ether to the second perfluoroalkylvinyl ether isabout 5% to about 25%.
 30. A molded article comprising the curedperfluoroelastomeric composition according to claim
 21. 31. The moldedarticle according to claim 30, wherein the molded article is an O-ring,a seal or a gasket.
 32. The molded article according to claim 30,wherein the molded article is bonded to a surface comprising a metal ora metal alloy.
 33. The molded article according to claim 32, wherein themolded article is bonded to surface of a door for sealing asemiconductor-processing chamber.
 34. A method for making a curedperfluoroelastomeric composition comprising: (a) preparing a curableperfluoroelastomeric composition by combining: (i) a first curableperfluoropolymer comprising tetrafluoroethylene, a first perfluoroalkylvinyl ether and at least one first cure site monomer having a cure site,wherein a molar ratio of the tetrafluoroethylene to the firstperfluoroalkyl vinyl ether is about 0 to about 100 to about 65:35 in theperfluoropolymer; (ii) a second curable perfluoropolymer comprisingtetrafluoroethylene, a second perfluoroalkylvinyl ether which may be thesame or different from the first perfluoroalkylvinyl ether, and at leastone second cure site monomer having a cure site which may be the same ordifferent from the at least one first cure site monomer, wherein a molarratio of the tetrafluoroethylene to the second perfluoroalkylvinyl etheris about 65:35 to about 95:5 in the polymer; and (iii) at least onecurative capable of curing the cure site of the at least one first curesite monomer and the cure site of the at least one second cure sitemonomer; and (b) curing the first and second curable perfluoropolymersin the perfluoroelastomeric composition to form a curedperfluoroelastomeric composition.
 35. The method according to claim 34,wherein the cured perfluoroelastomeric composition comprises abenzoimidazole cross-linking structure.
 36. The method according toclaim 34, wherein step (b) further comprising curing the curableperfluoroelastomeric composition at a temperature of about 150° C. toabout 250° C. for about 5 min to about 40 min.
 37. The method accordingto claim 36, where step (b) further comprises a postcure at atemperature of about 250° C. to 320° C. for about 5 to about 48 hours.38. The method according to claim 34, wherein step (a) further comprisescombining (iv) at least one additive into the curableperfluoroelastomeric composition.
 39. The method according to claim 34,wherein the method further comprising forming the curableperfluoroelastomeric composition into a molded article while curing thecurable perfluoroelastomeric composition.